test(paste): pin the main pane's keydown hand-off, and say which engines still get two pastes (#799)

The two edits promised in the review of #799:

- The main pane's Ctrl+V branch hands the keydown to the paste trap, and
  nothing tested that call: with it reverted to `_handleImagePaste()` every
  test still passed and Firefox would paste twice again. A source pin now
  fails on that, like the Ctrl+C one in terminal-copy-clean.test.ts.
- architecture-invariants and src/web/CLAUDE.md described the key's own paste
  as reaching the trap in every browser. Since #799 that is Chromium and
  WebKit only: in Firefox the trap cancels the keydown.

Co-Authored-By: Claude Fable 5.2 <noreply@anthropic.com>

src/web/CLAUDE.md

@@ -20,7 +20,7 @@
 
 **OSC 52 clipboard** (`_installOsc52Clipboard`, terminal-ui.js; main terminal + every `TerminalTile`): a program in the PTY (Claude Code's `/copy`, tmux yanks, vim) sets the browser clipboard with `ESC ] 52`. ⚠️ Writes only: a `52;?` read query is always refused, never answered. ⚠️ A replay must never copy: `chunkedTerminalWrite` strips every OSC 52 (`OSC52_STRIP_RE`, constants.js) because xterm parses after `_isLoadingBuffer` is cleared, so the flag alone does not hold; a tile gates on its own `_bufferLoading`, which does. ⚠️ One copy arrives up to three times (Claude's own OSC 52, `tmux load-buffer -w`, set-clipboard forwarding), so identical text within `OSC52_DEDUPE_MS` is dropped. ⚠️ Every tab on the session receives it; only the focused one opens the manual-copy fallback. ⚠️ Restore prior focus after `_copyText` (its execCommand fallback focuses a temp textarea). Tests: `test/terminal-osc52-clipboard.test.ts` (replays drive the real `chunkedTerminalWrite` over `@xterm/headless`).
 
-**Ctrl+V paste trap** (`image-input.js`): `Ctrl+V` routes through `_handleImagePaste()`, which focuses a hidden `contenteditable` trap and reads the clipboard from the paste event landing there; images upload and their paths are typed in, plain text is a Codeman-built bracketed paste handed to that pane's terminal via `terminal.input(framed)` (strip nested 200/201 markers, newlines to `\r`, wrap CSI 200~/201~) because `terminal.paste()` drops those markers after a replay clears xterm's DECSET 2004 mirror (#716). `input()` fires onData as user input, so the main pane's bracketed-paste branch and a tile's `_onTerminalData` deliver the frame, including the local-echo flush (#219). The terminal is only refocused. ⚠️ **The trap must consume exactly ONE paste event** (Firefox delivers two per keypress: the `execCommand('paste')` event and the keydown's default action); the one-shot flag lives on the trap, never on a browser check. ⚠️ **Once `execCommand` has delivered, the trap cancels the keydown** (`target.keyEvent`, passed by both the main pane and a tile): Firefox's second paste is a separate task that races the trap's removal, and when it loses it lands on xterm's textarea and pastes again, which the flag cannot see. Never cancel the keydown unconditionally; Chromium and WebKit get their only paste from its default action. ⚠️ Do not remove the `execCommand('paste')` call: on some mobile engines it is the only route into the trap, and the trap is the only place image blobs are read. Tests: `test/image-paste-trap.test.ts`. → [architecture-invariants#terminal-paste-ctrlv](../../docs/architecture-invariants.md#terminal-paste-ctrlv)
+**Ctrl+V paste trap** (`image-input.js`): `Ctrl+V` routes through `_handleImagePaste()`, which focuses a hidden `contenteditable` trap and reads the clipboard from the paste event landing there; images upload and their paths are typed in, plain text is a Codeman-built bracketed paste handed to that pane's terminal via `terminal.input(framed)` (strip nested 200/201 markers, newlines to `\r`, wrap CSI 200~/201~) because `terminal.paste()` drops those markers after a replay clears xterm's DECSET 2004 mirror (#716). `input()` fires onData as user input, so the main pane's bracketed-paste branch and a tile's `_onTerminalData` deliver the frame, including the local-echo flush (#219). The terminal is only refocused. ⚠️ **The trap must consume exactly ONE paste event** (Firefox delivered two per keypress, the `execCommand('paste')` event and the keydown's default action, until the trap began cancelling the keydown, and the flag still guards a browser that sends both); the one-shot flag lives on the trap, never on a browser check. ⚠️ **Once `execCommand` has delivered, the trap cancels the keydown** (`target.keyEvent`, passed by both the main pane and a tile): Firefox's second paste is a separate task that races the trap's removal, and when it loses it lands on xterm's textarea and pastes again, which the flag cannot see. Never cancel the keydown unconditionally; Chromium and WebKit get their only paste from its default action. ⚠️ Do not remove the `execCommand('paste')` call: on some mobile engines it is the only route into the trap, and the trap is the only place image blobs are read. Tests: `test/image-paste-trap.test.ts`. → [architecture-invariants#terminal-paste-ctrlv](../../docs/architecture-invariants.md#terminal-paste-ctrlv)
 
 **File Viewer text view: rendered markdown + Lines/Wrap toggles** (`_renderFilePreviewText()` in panels-ui.js): a `.md`/`.markdown` opens RENDERED by default with an `MD` pill back to source; the plain-text view has `Lines` (CSS-counter gutter) and `Wrap` toggles. ⚠️ ONE markdown pipeline: the viewer calls `_renderMarkdown(text, { breaks: false })` (marked + the DOMPurify allowlist, the Response Viewer's; chat keeps the default `breaks: true`, a file must not turn every hard wrap into a `<br>`) and binds the Response Viewer's click delegate (`_bindResponseViewerInteractions`) on the preview body for code-copy buttons and path links; never a second parser or handler. ⚠️ The document is built inside a `<template>` (a detached div with `innerHTML` set starts fetching every `<img src>` before the rewrite), then `_rebaseFilePreviewMarkdownRefs()` points relative images at the workspace-confined `file-raw` under the document's directory and root-relative ones under the workspace root (never a widened route; a failed load degrades to alt text), after `decodeURIComponent`ing the ref and dropping `?query`/`#fragment` (marked percent-encodes destinations, and the route encodes again), and turns workspace links into `a.rv-path` carrying `data-session-id` for the delegate (the linkifier's absolute paths get it too), stripping the `target` marked gave them. ⚠️ A preview opened by attachment id under a bare file name (attachment cards, history drawer: the registry keeps no relative path) has no directory, so its workspace refs degrade (images to alt text, links to their text), never resolve against the workspace root. ⚠️ The container carries `data-i18n-skip` or the translator rewrites the document's prose. ⚠️ Toggles are per-device localStorage keys (`codeman:filePreview*`), never `SettingsUpdateSchema`; Lines/Wrap are class flips on the ONE `<pre>`, with rules scoped `.file-preview-body > pre.file-preview-text` so they never leak into the document's code blocks. Markdown fetches `lines=10000` (the route ceiling), other text keeps 500. ⚠️ `md`/`markdown` are IN `FILE_PREVIEW_EXTENSIONS` (owner decision 2026-10-13): a markdown path clicked or tapped in the TERMINAL (main pane, grid tiles and split Pane B share `registerFilePathLinkProvider`) opens this rendered view like every other surface, never the streaming log viewer; other in-workspace text keeps the tail viewer (live follow). The terminal pattern links `.markdown` and `.htm` too. ⚠️ **Right-to-left text** (#715) has three parts on that one pipeline: `_renderMarkdown` pins `pre, code` to `dir="ltr"`, `_linkifyFilePaths` pins the anchors it builds the same way (`dir="auto"` skips a descendant that carries a `dir`, so `npm install` or a path at the head of a Persian sentence does not decide its direction; a markdown link's label is prose and stays unpinned), and `_applyBlockDirection()` gives each OUTERMOST prose block `dir="auto"`, keeping a `dir` the agent wrote and what it covers. ⚠️ That pass runs LAST, on the DOM, in both consumers (`_buildResponseViewerMessage`, `_renderFilePreviewText`), never in `_renderMarkdown` (its string must hold no `dir="auto"`) and never inside the linkifier (which returns early on a stale constants.js): an element already carrying `dir="auto"` re-resolves its direction on every insertion under it, so a code-only or path-only document went quadratic and a 200 KB list froze the tab for 40 s. ⚠️ The `.rv-text` block rules use logical properties (`padding-inline-start`, `border-inline-start`, `border-inline-end`, `text-align: start`, logical corner radii), never physical left and right, or an RTL block keeps its bullets and quote bar on the wrong side. The terminal pane is out of reach: xterm.js has no RTL support (xtermjs/xterm.js#701). Tests: `test/file-preview-markdown.test.ts`, `test/response-viewer-rtl.test.ts`. → [architecture-invariants#file-viewer-text-view-rendered-markdown-and-text-toggles](../../docs/architecture-invariants.md#file-viewer-text-view-rendered-markdown-and-text-toggles)