chore(web): remove the Ralph wizard and its plan-generation UI

The wizard's only entry point was the "Start Ralph Loop" button on the
start screen, removed in 1.50.0, so none of this could be opened or
triggered from the app any more:

- ralph-wizard.js (the wizard, plan generation flow and the floating plan
  subagent windows) and the #ralphWizardModal markup;
- the "Plan Wizard Agents" section of the monitor panel with its cancel
  button, and the five plan:* SSE handlers that only fed these surfaces;
- the wizard branches in the subagent window code: connection lines to
  the wizard and to plan agents, window placement beside the wizard, and
  the wizard cleanup on reconnect. The ordinary path (agent window to its
  parent tab) is unchanged, only un-nested;
- the wizard's state on the app object and its z-index constant;
- its styles: 67 classes, three keyframes and a second identical
  @keyframes spin.

What stays: the Ralph panel, the Ralph tab in session options, the plan
routes (/api/generate-plan, /api/generate-plan-detailed,
/api/cancel-plan-generation, the ralph-wizard file routes) and the
plan:* SSE events, which are part of the public API. A client that
starts plan generation over the API still gets its events; the page no
longer draws anything for them.

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

docs/architecture-invariants.md

@@ -1339,7 +1339,7 @@ Tests: `test/mobile-prompt-composer.test.ts` (in the CI gate, deliberately not u
 
 ### Z-index layers
 
-**Z-index layers**: subagent windows (1000), split picker menu (1000, `.split-picker-menu`), Tiles count menu (1000, `.tile-count-menu`), the closing grid's still copy (`.tile-grid-ghosts`, z-index 3 inside `.main`, over the single view coming back; hidden under `.main.webview-active`), plan agents (1100), mobile/tablet fixed header (1200, `mobile.css`), modals on ≤768px (1300 — must beat the fixed header or the modal close button is buried), log viewers (2000), connection-loss overlay (2500, above the fixed header and modals), image popups (3000), response viewer (5000, backdrop 4999), folder grid (5090, `#folderGridOverlay` — above the response viewer a folder link opens it from, below the file preview its tiles open, so a tile's preview and its ←/→ paging sit on top of the grid), file-preview overlay (5100 — must outrank the response viewer, which can launch it; at its old 2000 a path clicked in the chat opened BEHIND the chat), toasts/path picker (10000+, deliberately above the preview), the custom-model center-status banner (10001, `.center-status-banner` — `[hidden]` must re-assert `display: none` over its own `display: flex`, same trap as `.home-sessions[hidden]`, or `dismiss()` leaves an invisible click-blocker dead centre on screen), the swap-confirm and context-warning modals (10010, `#customModelSwapConfirmModal`/`#customModelContextWarningModal` — must clear both the plain `.modal` z-index of 1000 and the center-status banner it can appear over), terminal touch-selection bar (900 — above terminal content and the local-echo overlay, deliberately BELOW floating agent windows so it can never cover their controls), local echo overlay (7), iOS IME composition preview (EFFECTIVE layer depends on its home: with local echo on it is part of the local echo overlay at 7, drawn by `setComposition()` as an underlined tail after the pending text; with local echo off it is a span at z-index 6 inside `.xterm-helpers`, but `.xterm-helpers` is its own z-index 5 stacking context, so the span's effective layer is 5. That is below the overlay's 7, which is why the span cannot be used while the overlay holds text: typed text never reaches the PTY before Enter, the PTY cursor that places the span stays at the prompt start, and the overlay's opaque line div covers it).
+**Z-index layers**: subagent windows (1000), split picker menu (1000, `.split-picker-menu`), Tiles count menu (1000, `.tile-count-menu`), the closing grid's still copy (`.tile-grid-ghosts`, z-index 3 inside `.main`, over the single view coming back; hidden under `.main.webview-active`), mobile/tablet fixed header (1200, `mobile.css`), modals on ≤768px (1300 — must beat the fixed header or the modal close button is buried), log viewers (2000), connection-loss overlay (2500, above the fixed header and modals), image popups (3000), response viewer (5000, backdrop 4999), folder grid (5090, `#folderGridOverlay` — above the response viewer a folder link opens it from, below the file preview its tiles open, so a tile's preview and its ←/→ paging sit on top of the grid), file-preview overlay (5100 — must outrank the response viewer, which can launch it; at its old 2000 a path clicked in the chat opened BEHIND the chat), toasts/path picker (10000+, deliberately above the preview), the custom-model center-status banner (10001, `.center-status-banner` — `[hidden]` must re-assert `display: none` over its own `display: flex`, same trap as `.home-sessions[hidden]`, or `dismiss()` leaves an invisible click-blocker dead centre on screen), the swap-confirm and context-warning modals (10010, `#customModelSwapConfirmModal`/`#customModelContextWarningModal` — must clear both the plain `.modal` z-index of 1000 and the center-status banner it can appear over), terminal touch-selection bar (900 — above terminal content and the local-echo overlay, deliberately BELOW floating agent windows so it can never cover their controls), local echo overlay (7), iOS IME composition preview (EFFECTIVE layer depends on its home: with local echo on it is part of the local echo overlay at 7, drawn by `setComposition()` as an underlined tail after the pending text; with local echo off it is a span at z-index 6 inside `.xterm-helpers`, but `.xterm-helpers` is its own z-index 5 stacking context, so the span's effective layer is 5. That is below the overlay's 7, which is why the span cannot be used while the overlay holds text: typed text never reaches the PTY before Enter, the PTY cursor that places the span stays at the prompt start, and the overlay's opaque line div covers it).
 
 ## Security layers