Finish the .har waterfall on pull #10953: the docs sentence and the four tests sentinel asked for #11019

Replaces #10936. The renderer, escaping, caps, fallback and terminal door on pull #10953 were judged sound by juniper and sentinel; two asks remain. Continue on that pull's branch, do not restart.

Done when:

• [ ] docs/features/file-har.md says the page prints "N more headers not shown" (it does not leave the count out), and adds one line: the terminal workspace opens a .har as the same table, same row cap, s for source.
• [ ] test/render-har.test.ts covers: the 50-header cap and its "more headers" line; the 2,000-character text cap; statusText escaping (<script> in statusText arrives escaped); the terminal falling back to source for a malformed HAR.
• [ ] The stale not.toContain("aria-label=\"starts") assertion is removed.
• [ ] bun test test/render-har.test.ts test/render-kinds.test.ts and bun scripts/design-lint.ts pass.

Files: docs/features/file-har.md, test/render-har.test.ts. Risk: none beyond the pull; no new behaviour.

Parked by the crew: the run ended without a pull: declined: the code this issue builds on isn't reachable from my branch. src/web/render/har.ts, test/render-har.test.ts and docs/features/file-har.md don't exist on main or on my branch. Pull #10953's he

Parked by the crew: the run ended without a pull: declined: the code this issue builds on isn't reachable from my branch. src/web/render/har.ts, test/render-har.test.ts and docs/features/file-har.md exist on neither main nor my branch (scout/11019-…,

Parked twice since a person last spoke here, so it is the planner's now. Every reason:

1. the run ended without a pull: declined: the code this issue builds on isn't reachable from my branch. src/web/render/har.ts, test/render-har.test.ts and docs/features/file-har.md don't exist on main or on my branch. Pull #10953's he
2. the run ended without a pull: declined: the code this issue builds on isn't reachable from my branch. src/web/render/har.ts, test/render-har.test.ts and docs/features/file-har.md exist on neither main nor my branch (scout/11019-…,

The planner splits it, replaces it with a fresh issue, or defers it; a person can also say what to try. Nothing starts here until then, and the board lists it.

Dropped: the work it names exists only on pull #10953's branch, which is not on origin, so every fresh builder declined (twice). The two asks are restated on #10953 as one concrete change for its author, who can push to that branch; that pull is where it finishes.