fix(vite): apply app.css before the app entry on HMR dev boots - #11522

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What is the current behavior?

On the deterministic dev-session (HMR) boot path, the seeded app.css is only applied after __NS_HMR_BOOT_COMPLETE__ flips: the boot poller in the /__ns_dev__/client bootstrap calls __nsBrowserRuntimeReplaySeededCss(), which lazily installs installHttpCoreCssSupport and then restyles the mounted roots.

So the first page is built and laid out with no app CSS, then restyled. Anything that caches measurements on first layout keeps the unstyled sizes. The visible case is an iOS ListView: cell heights are cached in _heights on first measure, so with Tailwind p-4 on the row label the rows stay at their unpadded height (61px vs 161px measured) even though color/font/padding are applied to the labels afterwards. Pages navigated to after boot look fine, which makes it look like only the first page is "unstyled".

Non-HMR builds don't have this problem: helpers/main-entry calls addTaggedAdditionalCSS(ast, 'app.css') before app code runs.

What is the new behavior?

The client bootstrap (which session-bootstrap imports before the app entry, and which already imports the /ns/core bridge) statically imports installHttpCoreCssSupport from entry-runtime and calls it at top level. The seeded app.css AST lands in the /ns/core realm before the first page is built, matching non-HMR builds.

• __NS_HMR_HTTP_APP_CSS_APPLIED__ is set, so the existing post-boot replay becomes a no-op but stays as a fallback if the early install can't find a CSS API.
• __NS_HMR_APPLY_CSS__ / __NS_REGISTER_CSS__ are now installed before the entry too. Component / .css module styles register immediately instead of queueing in __NS_PENDING_CSS__ until post-boot; the full client's installCssRegister keeps the existing applier (same tagged remove+add, restyle only after boot).
• Rule order now matches production: app.css selectors precede component styles in the additional-selector list (previously in HMR, app.css was appended after styles registered during boot).

Verified on an Angular + Tailwind app (iOS simulator): first-page ListView rows render with correct padding on cold boot, and live app.css edits still hot-apply.