fix(copilot): Free plan usage, tall answers in agent read, page-key fallback, review nits

Review of 8659ba25..be987fbb:

- Usage: a Free account answers premium_interactions {entitlement: 0, remaining: 0,
  percent_remaining: 0, unlimited: false, has_quota: false}, which read as 100% used. The parser now
  returns null when has_quota is false or the entitlement is not positive, with that payload as a
  fixture. Free meters chat (200) and completions (2000) too, so the comment no longer says they
  are unlimited on every plan.
- agent read: rows were skipped until a `❯ <prompt>` row, so an answer taller than the pane
  (prompt scrolled off the top) read as "". With no prompt row AND no banner / trust dialog on
  screen, the rows above the composer are now the tail of the last answer. Text typed in the
  composer (a prompt-shaped row between the two rules) is not a prompt row.
- Page keys: measured on 1.0.95 in tmux that Copilot pages on PageUp/PageDown (three PageUp moved
  lines 109-140 to 010-042, PageDown returned) as well as on SGR wheel reports, so copilot joins
  claude and opencode in _localScrollbackIsHollow(); the stale-tracking-flag fallback the comment
  and docs describe is now true, for the main pane and a TerminalTile (same function), with tests.
- X-GitHub-Api-Version is 2022-11-28, a version GitHub supports (verified against the live
  endpoint); readPlanUsageTelemetryEnabled() is checked before isCopilotAvailable() so a switched-off
  chip skips the resolver probe too.
- Palette label for Copilot in panels-ui.js; stale comments in types/session.ts and stock.ts.
- Docs: Past Sessions continues with --continue (resumeSessionId is for API callers), nothing sets
  continueSession on a respawn, and only a tab name the user set is passed as --name; the usage
  wording for Free; the wheel and mouse-strip paragraphs in CLAUDE.md and
  architecture-invariants; the changeset describes the whole feature.

.changeset/cli-copilot.md

@@ -2,4 +2,4 @@
 'aicodeman': minor
 ---
 
-GitHub Copilot CLI is a run mode. It appears in the Run menu, the welcome screen and the cron agent list once `copilot` is installed, runs in tmux like the other agent CLIs, reports working and idle from its `Working` footer, shows the model it reads off its footer on the tab, and is listed in CLI management with an install command (`npm install -g @github/copilot`). It takes the same launch options as the other agent CLIs: a `copilotConfig` on the session create and quick-start bodies with `model` (`--model`), `resumeSessionId` (`--resume`), `continueSession` (`--continue`) and `allowAll` (`--yolo`, which the Run button sends and which is clamped off for non-granted multi-user owners), history resume, and a `GET /api/copilot/status` probe.
+GitHub Copilot CLI is a run mode. It appears in the Run menu, the welcome screen and the cron agent list once `copilot` is installed, runs in tmux like the other agent CLIs, reports working and idle from its `Working` footer, shows the model it reads off its footer on the tab, and is listed in CLI management with an install command (`npm install -g @github/copilot`). It takes the same launch options as the other agent CLIs: a `copilotConfig` on the session create and quick-start bodies with `model` (`--model`), `resumeSessionId` (`--resume`), `continueSession` (`--continue`, which Past Sessions sends) and `allowAll` (`--yolo`, which the Run button sends and which is clamped off for non-granted multi-user owners), a tab name you set yourself as `--name`, Custom Model Endpoints through Copilot's BYOK variables, MCP sync of its `mcp-config.json`, and a `GET /api/copilot/status` probe. A plain drag selects text (Auto Copy works) while the wheel and phone swipes scroll its transcript, `codeman agent spawn` waits for its composer, `codeman agent read` returns its last answer, and the header plan-usage chip gains a Copilot row with the month's premium-request quota (not shown for Free or unlimited plans).