chore(performance): commit the initial-bytes baseline and ratchet checker (#1693)

Second step of the performance-journeys ratchet, stacked on #1692 (merge that first; this PR retargets to `master` automatically).

- `tools/performance/journey-baselines.json`: J1 `launch` / `renderer.initialBytes` = **2,739,510 bytes**, the ubuntu runner's production build of `apps/web` at this content (after #1692 stopped bundling `package.json` into `main.js`). A local macOS build of this pre-#1695 code is 2 bytes smaller in `main.js` (the eager locale imports); once #1695 removes them the two are byte-identical. Correction to an earlier version of this description: the "556-byte macOS vs Linux difference" was almost entirely `package.json` text embedded in `main.js`, which moved with every script edit in this stack, plus this 2-byte residue. The runner is the canonical measurer; the CI run on the stacked #1694 branch (this content plus the job) is where the number is confirmed.
- `tools/performance/check-journey-ratchet.mjs` compares a journey summary with the baselines: a counter above its value fails (exact, no slack), wall-clock entries fail above `value × toleranceRatio`, a baseline without a measurement fails so dropping a measurement cannot disable the ratchet, values below baseline print a "tighten" hint, and measured counters without a baseline are noted only. After review: checking nothing (empty file, or `--only` naming a missing entry) fails; a counter is read only from `counters` and a wall-clock entry only from `wallClock`; the repeatable `--only <journey>/<counter>` flag scopes a check.
- Root scripts: `perf:initial-bytes:check` (measures into its own `dist/performance/initial-bytes.summary.json`, then checks `--only launch/renderer.initialBytes`) and `perf:ratchet:check` (full check); `perf:tools:test` runs both test files, as does `pnpm nx test performance-tools`.
- `docs/architecture/performance-journeys.md` gains the Ratchet section (file format, rules, "baselines only move down"); the validation map lists the check.

The CI job that runs the check on every PR is #1694; C1 (lazy Angular date locales, #1695) then lowers the baseline with the measured output as evidence.

Note: `ci.yml` only triggers on pull requests targeting `master`, so this stacked PR shows no Actions runs until #1692 merges. The evidence runs above were dispatched with `gh workflow run ci.yml --ref <branch>`.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

docs/architecture/validation-map.md

@@ -157,12 +157,15 @@ audit.
 
 ```bash
 pnpm nx build web
-pnpm run perf:initial-bytes
+pnpm run perf:initial-bytes         # breakdown only
+pnpm run perf:initial-bytes:check   # measure, then compare with the committed baseline
 pnpm nx test performance-tools
 ```
 
 `perf:initial-bytes` reads the built `dist/apps/web/index.html` and sums the
-bytes on the initial path (the J1 counter `renderer.initialBytes`). The
+bytes on the initial path (the J1 counter `renderer.initialBytes`).
+`perf:initial-bytes:check` then fails if the value exceeds
+`tools/performance/journey-baselines.json`; baselines only move down. The
 contract, what counts and how to add a counter are in the
 [performance journeys](performance-journeys.md) document.