Fetch the citation dialog on first open; hold the embed to a fixed budget (closes #356)

[adamjohnwright]

The last part of #356.

The citation dialog loads when it's first opened.

• The embed provides CitationService but never shows its dialog. The service's MatDialog and CitationComponent imports were carrying Material's dialog code into the embed's first load.
• Both are now imported when the dialog first opens. The Pathway Browser's and the site's buttons report a failed fetch.
• The embed's initial load goes from 1,366 KB to 1,324 KB, with no dialog code left in it.

Correction to what I first proposed: svg-pan-zoom (illustrations) and svgcanvas (downloads) were already loaded on demand in the embed, through the lazy illustration component. My earlier per-package totals had mixed on-demand chunks into the first load. The slider and drag-and-drop are the zoom control and the legend drawer, both visible in the first view, so they stay.

The "Cite us" button had no accessible name. Nothing tested the dialog, so e2e/citation-dialog.spec.ts now does: the Pathway Browser's "Cite us" and the site-wide "Cite Us".

• Writing the test showed the Pathway Browser's button had only a tooltip, so a screen reader announced an unnamed button. It now has aria-label="Cite us", and the test finds it by that name. I checked the test fails without it.
• The pathway citation request carries today's date (?dateAccessed=), so no recording can match it. The test answers it in the service's own shape, taken from beta.
• The recordings were scanned for server version strings; there are none.

SC-004 is now a fixed budget.

• It said "less than a third of the full site", but that ratio moves whenever the site changes: slimming the site raised the bar by about 50 KB while the embed was being slimmed.
• It now names an absolute budget, set just above today's 1.36 MB initial so the embed can only shrink: warn 1.4 MB, error 1.45 MB in angular.json, for production and beta.
• I checked that a 1.3 MB budget fails the build.
• spec.md and tasks.md record the change and why.

Where #356 ends up (with #432, reactome/ngx-reactome-base#15 + #434 and #433): the router, lodash, vectorious and the dialog are all out of the first load. Initial JavaScript went from 1.58 MB to 1.36 MB.

Checks: unit tests (729) pass; the citation e2e tests (2) pass; preflight passes; lint is unchanged.

Closes #356.

🤖 Generated with Claude Code

[adamjohnwright]

Review (subagent, adversarial): no defects. MatDialog is providedIn: 'root', so resolving it through the service's injector gives the same instance and overlay container as before, on the site and in the embed; both callers handle the promise; the route pattern matches the dated request; recordings carry no server/version headers; the budget is enforced by CI and preflight (build:embed, production), with 1,355,809 bytes against 1.4 MB / 1.45 MB in Angular's 1000-based units. Fixed in the latest commit: a second click while the dialog's code loads no longer opens a second dialog (in-flight guard plus a dialog id; the new e2e test fails without it, two dialogs), the unused afterClosed() is gone, and SC-004 says which figure the budget checks.