[test-recorder] Add regression tests for UX-critical behaviors (standby start, inspector suppression, reassurance copy, tag instructions)

### Problem
Several behaviors that fixed real user-testing failures are protected only by prose, not tests:

- Recorder starts in standby (not auto-recording) — `src/recorder/template.ts:74-85`; copy in `src/recorder/runner.ts:105-117` and `src/commands/guide.ts:62-66` must stay consistent with it.
- Inspector suppression via `PW_CODEGEN_NO_INSPECTOR=1` — `src/recorder/runner.ts:153-156`.
- Contributor-reassurance copy ("recordings can't be wrong", maintainers will tidy) — `src/commands/record.ts:248-260,788-793`; `src/commands/guide.ts:47-55`.
- Tag-multiselect keyboard instructions (SPACE to select, ENTER when done) — `src/commands/record.ts:475-488`.

Any of these can be silently removed in a refactor and would regress exactly the failures observed in user testing.

### Suggested fix
Add snapshot/behavioral tests: assert the codegen template starts in standby, assert the env var is passed to Playwright, and snapshot the reassurance/keyboard-instruction strings.

_Line references are against branch `cb/comfy-test-usability` (PR #15837); adjust after merge._