fix(build,docs): dependency preflight before the build wipes dist, docs drift for 1.40.0

- scripts/build.mjs resolves exceljs/dist/exceljs.min.js and fflate first,
  before tsc and before rm -rf dist/web/public. A tree whose node_modules
  predate those devDependencies (pulled but never ran npm install) used to
  fail in prepare-spreadsheet-assets.mjs with the live dist assets already
  deleted, so the running server served an index.html whose hashed files
  were gone. It now exits 1 with "run `npm install` first", nothing touched.
  test/spreadsheet-assets.test.ts pins the order, that the list covers every
  require.resolve in the prepare script, and runs a relocated copy of the
  build to prove the exit and message.
- CLAUDE.md: the header visibility rule's stock desktop default now lists
  Tiles (1180px and wider), which ships ON on desktop.
- docs/wiki/Agent-CLIs.md: "Before 1.36.0" becomes "Before 1.40.0" (four
  places); 1.36.0 never ships.
- docs/wiki/Home.md: the "Everything in the manual" index lists Tile Grid
  and Custom Model Endpoints, matching the sidebar. test/wiki-home-index
  fails when a sidebar page is missing from that index.
- docs/wiki/Tile-Grid.md: the Tiles default is off on tablets too since the
  touch-primary default landed, not only on phones.
- docs/browser-testing-guide.md: the fixed port table and new WebServer(PORT)
  snippet give way to the port-0 pattern (new WebServer(0, false, true),
  server.boundPort) that test/test-ports-guard.test.ts enforces; the
  examples that opened localhost:3000, the live instance, use BASE_URL.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -353,7 +353,7 @@ Frontend JS modules have `@fileoverview` with `@dependency`/`@loadorder` tags. L
 
 **Settings surface** (`#appSettingsModal` + `#sessionOptionsModal` + `#createCaseModal`): one `set-*` language shared through a single `:is(...)` id scope in styles.css. App Settings' rail is a table of contents over ONE scrolling document (`switchSettingsTab` scrolls); Session Options and Add Case really switch (`switchOptionsTab` / `switchCaseModalTab`), and their larger per-modal size blocks are the design, not drift. ⚠️ **The load/save contract is `getElementById` by id**: renaming or dropping a control id silently stops it loading or saving. ⚠️ The Session Options "Session" entry still keys off `context` (label-only rename). ⚠️ Add Case keeps its legacy `.form-row` markup via an adapter; every `<details>` there needs `.set-adv-chev` plus both marker suppressions. ⚠️ Model cards and the effort segment are views over hidden `<select>`s, which stay the source of truth. ⚠️ `.modal-tabs*` classes are retired; `admin-ui.js` needs `.set-rail-items` + `.set-doc` to survive any restructure. Guard: `test/app-settings-structure.test.ts`. → [architecture-invariants#settings-surface-app-settings-session-options-add-case](docs/architecture-invariants.md#settings-surface-app-settings-session-options-add-case)
 
-**Header button visibility**: most header controls are opt-in and hidden by a marker class (`btn-multimonitor--hidden`, `btn-response-viewer-header--hidden`, `btn-file-viewer--hidden`, `btn-cron--hidden`, and the desktop-gated `btn-split--hidden` / `btn-tile-grid--hidden`, which also need a `@media (max-width: 1179px)` backstop) that `applyHeaderVisibilitySettings()` (settings-ui.js) toggles after settings load; the multi-monitor button is instead stripped at render by `renderIndexHtml`. ⚠️ Hiding must go through the marker class: the base rules are `display:inline-flex !important`, so an inline style cannot override them. Current desktop default is WS/CPU/MEM + File Viewer + gear, with the token chip and lifecycle-log button OFF. ⚠️ New header controls must not leak onto phones; `test/mobile-header-buttons-policy.test.ts` is the static guard. → [architecture-invariants#header-button-visibility-multi-monitor-response-viewer-file-viewer-cron](docs/architecture-invariants.md#header-button-visibility-multi-monitor-response-viewer-file-viewer-cron)
+**Header button visibility**: most header controls are opt-in and hidden by a marker class (`btn-multimonitor--hidden`, `btn-response-viewer-header--hidden`, `btn-file-viewer--hidden`, `btn-cron--hidden`, and the desktop-gated `btn-split--hidden` / `btn-tile-grid--hidden`, which also need a `@media (max-width: 1179px)` backstop) that `applyHeaderVisibilitySettings()` (settings-ui.js) toggles after settings load; the multi-monitor button is instead stripped at render by `renderIndexHtml`. ⚠️ Hiding must go through the marker class: the base rules are `display:inline-flex !important`, so an inline style cannot override them. Current desktop default is WS/CPU/MEM + File Viewer + Tiles (1180px and wider) + gear, with the token chip and lifecycle-log button OFF. ⚠️ New header controls must not leak onto phones; `test/mobile-header-buttons-policy.test.ts` is the static guard. → [architecture-invariants#header-button-visibility-multi-monitor-response-viewer-file-viewer-cron](docs/architecture-invariants.md#header-button-visibility-multi-monitor-response-viewer-file-viewer-cron)
 
 **Gesture control** (camera hand-tracking overlay, opt-in, default OFF): `CODEMAN_GESTURE=1` makes the feature *available*; `gestureControlEnabled` turns it on. The bundle is injected by `renderIndexHtml` only when enabled, which is why that method is `async` and reads settings with `readSettings(true)` (a fresh read: a post-save reload lands inside the 2s cache TTL and would otherwise render the pre-toggle state). **Source lives in `packages/gesture-control/`; edit there, run `npm run build:gesture`, and commit the regenerated bundle** because dev serves the committed bundle with no runtime bundler. The MediaPipe wasm + model are fetched separately and gitignored. ⚠️ Keep `MP_VERSION` in `fetch-gesture-assets.mjs` in sync with `@mediapipe/tasks-vision`. → [architecture-invariants#gesture-control-the-source-package](docs/architecture-invariants.md#gesture-control-the-source-package)