refactor(settings): remove page overlap, files at once, highlight code and chat page keys - #1104

Carries this branch's own changes (92c1226..a09cc2e) onto main after #1099 and #1104 were squash-merged; telemetry/worker.ts, shared/telemetry.ts and deployed.json are unchanged from the deployed receiver.

#1105)

Stacked on #1104 (itself on #1099); retarget to `main` once they merge.

## Change

The settings snapshot now covers every setting the app keeps after #1099
and #1104, so a later trim can be decided from data:

- **Added:** `paletteLight`, `paletteDark`, `uiFontSize` (11–20, or
`null` for the screen's size), `diffStyle`, and `usageOrderCustom`, a
yes/no for whether the usage meters' accounts were put in an order of
the user's own (the accounts themselves are never sent, as for
`usageHiddenCount`).
- **Dropped:** the nine fields #1099 and #1104 kept sending as fixed
values (`terminalCursorStyle`, `terminalCursorBlink`, `narrowPaneFont`,
`showSuggestionChip`, `usagePace`, `highlightCode`, `pageOverlapRows`,
`chatPageKeys`, `attachLimit`). No released version sends a snapshot yet
(0.4.8 still sends `changed_settings`), so nothing in the field breaks.
- `palette` accepts only the three palettes the app still has.
- `TelemetrySourceSettings` no longer exempts the four settings it
listed as "not collected", so a new setting still needs an explicit
decision.

## Deployed

- Production D1: `ALTER TABLE events ADD COLUMN settings TEXT`
(telemetry/README.md). The table now has `settings`; all 1967 existing
rows were kept, with `settings` NULL.
- Worker deployed from this branch (version `84a7f138`), and
`telemetry/deployed.json` updated with `bun scripts/release-guards.ts
--worker-deployed`. A malformed snapshot posted to the live endpoint is
refused with 400.

## Validation

- `bun run check fast`: generated types, typecheck and build pass. Its
unit run caught the hard-coded key count in `api.test.ts` (53 → 49);
after that fix, `bun run test:unit` passes 3584, 0 fail.
- `telemetry/worker.test.ts` (full snapshot, legacy `changed_settings`,
real-table INSERT and the README queries), `server/telemetry.test.ts`,
`settings.test.ts` and `release-guards.test.ts` pass.

…age-key settings (#1110)

Docs-only follow-up to #1099, #1101 and #1104, from a post-merge review
of main 709fc70.

- DESIGN.md: drop the Contrast setting's stepper reset arrow and its
WCAG constraint bullet (the setting and its section went with #1099).
- DESIGN.md and the `SETTING_SCOPE` comment in `src/lib/settings.ts`:
code highlighting is no longer a shared setting (#1104 removed it).
- DESIGN.md: the plain chat page keys are always on, not opt-in (#1104).
- DESIGN.md: the pane header's ellipsis follows `any-pointer: coarse`,
matching #1101's touch-laptop fix.

No behavior change; no changelog fragment. Verified with `bun run
typecheck` and `HERDR_TEST_MODE=unit bun test ./src/conventions.test.ts
./scripts/conventions.test.ts` (0 fail).

#863, #864, #869 and #870 edited CHANGELOG.md directly, so the fold did not link them; #863's entry named the Files at once setting that #1104 removed (the app now takes up to 100 files).

#811 had landed under 0.4.7 by a merge; its entry now describes what survived #1104 (Mod+Shift+PageUp/PageDown, one line of overlap). The Hermes Stop note carries #1161, the held-input notes #972, and the folded message note no longer mentions Find, which #1140 removed.

…#1237) into next

Conflicts resolved in 24 files:
- Find in messages is gone upstream (devswha#1140): the comment-mode toggle takes its place at the
  chat's top right, and the transcript leaves room for it only while it shows.
- highlightCode is removed with upstream's settings cleanup (devswha#1104).
- The docked file panel (devswha#1224) gets the file comments: the dialog and the panel share the
  commentable body, the toggle and the viewer's props.
- submitNote/submitRefusal take upstream's `agent` first and the fork's `agentOnly` after it;
  SubmitOptions gains upstream's resendId/generation, so a held copy with comments resends
  agent-only under its resend id; the server's resend paths keep `typed: false`.
- Telemetry reports every setting except the fork's comment settings.