feat: collapsible per-job sections on the Deployment View

[kurok]

Closes #40.

One summary row per job — environment count, newest release anywhere, and a toggle — followed by that job's environment rows in their own tbody. A dashboard with many jobs × many environments stays scannable.

The upstream PR cannot be applied: it is against the 2020 code, bundles the getActions() fix we already have from #16, and puts the toggle logic in an inline <script> — which is exactly what JENKINS-74429 removed. The behaviour lives in dashboard.js on the existing delegated handler.

Two departures from the issue

It says to put .edb-collapsed in blink.css — but #42 deleted that stylesheet when the modal moved to core's dialog. Toggling the hidden attribute does the same job with no stylesheet to reintroduce, since browsers already style [hidden] as display: none.

It also suggests shipping chevron.svg; ionicons-api is already a dependency, so the chevron comes from there.

Degrades properly

Collapsing is client-side and the rows are always in the served HTML, so anything reading the page without running scripts still sees every deployment. Default is expanded up to five jobs, collapsed beyond, with the viewer's choice remembered in localStorage per job — wrapped in try/catch, since a private window throws there rather than returning null.

The toggle is a real <button> with aria-expanded and aria-controls, and the test asserts the attribute follows the visual state rather than merely being present.

Tests

• structure — one summary row and one environment section per job, and all four environment rows present in the HTML
• CSP — no inline event handlers anywhere in the table
• behaviour — clicking collapses that job and leaves the other expanded

The last one fails without the handler:

clickingTheToggleCollapsesOnlyThatJob
  clicking the toggle must collapse that job ==> expected: <true> but was: <false>

Verified against a real container before pushing

My last e2e assertion broke in CI because I reasoned about the markup instead of looking at it. Not this time:

e2e OK: dashboard shows both environments at 3.1.4, and the link redirects with its query string intact
edb-job rows: 2 · env sections: 2 · toggles: 4 · inline onclick: 0

Local mvn clean verify: 47 tests, green.

Not included

No view setting for the default state. The view's configure() still ignores its JSON (noted back in #16), so adding a persisted option means fixing that first — worth its own change rather than smuggling it in here.