fix(watch): warn when the project root matches a default ignore glob

[nikolas-sapa]

Fixes #23523.

Problem

resolveChokidarOptions prepends hardcoded default ignore globs — **/.git/**, **/node_modules/**, **/test-results/** (Playwright) — ahead of every user entry. Those globs are meant for tooling output inside a project, but they are anchored with **/, so they also match when the project root itself lives under an ancestor path segment of that name.

When that happens (e.g. a harness stages project copies inside a gitignored test-results/ directory — exactly what the glob exists to ignore), chokidar watches zero project directories: file edits fire no events, the module graph never invalidates, HMR never emits, and a full reload keeps serving pre-edit modules. There is no error surface — the failure looks like a downstream caching bug. And because anymatch ignores a path when any pattern matches, no server.watch.ignored entry can re-include the files.

The issue reporter confirmed watcher.getWatched() returns 0 directories over such a root, and that moving the project one directory up makes the watcher see everything again.

Change

Warn when the resolved project root matches one of the hardcoded default ignore globs, so a dead watcher is diagnosable instead of silent:

(!) The project root /home/user/test-results/my-project matches the default watch
    ignore pattern **/test-results/**.
    The dev server watcher will observe no files, so HMR will not work. Move the
    project out of that path.

Only the built-in defaults are checked — a user's own server.watch.ignored matching the root is their explicit choice, not a surprise, so it does not warn (there's a test for that). This is the lower-risk half of the reporter's suggestion (b); making the defaults removable (a) would be a larger API change and can be a follow-up.

Tests

Three cases in watcher.spec.ts: warns for a root under test-results/, does not warn for a normal root, and does not warn when only a user-supplied ignore matches the root. Reverting the source change turns the first test red while the two negative tests stay green. Full watcher.spec.ts passes (including the existing real-server watch tests).

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