feat(extraction+resolution): Astro support — frontmatter/template extraction + src/pages routes (#768) (#815)

.astro files were not indexed at all, leaving a typical Astro site mostly
invisible to search/impact/explore. New AstroExtractor (Svelte/Vue SFC
pattern): component node per file, TS frontmatter + <script> blocks
delegated to the TypeScript extractor, template {fn(...)} calls (incl. the
multiline `{posts.map((post) => (` opening line), PascalCase component-tag
references. New astroResolver: Astro global + astro:* virtual modules as
framework-provided, component resolution with the #764 ambiguity rule,
src/pages/ file-based routes ([param]→:param, [...rest]→*rest, _-prefixed
and *.config.* excluded). SFC languages now preload the TS/JS grammars
their extractors delegate to (a pure-SFC file set previously had none
loaded). Also fixes a pre-existing Svelte/Vue script-block off-by-one that
reported every script symbol one line low.

Validated per the playbook: stalux (the issue's repro) 54/54 .astro files
indexed, getIconNode found at its exact line, 14/14 routes, 93.0% fair
cross-file coverage; AstroPaper 27/27 components, 13/13 routes (underscore
dirs correctly excluded), explore connects page→Card→Datetime through the
jsx-render synthesizer; node/edge counts stable across re-syncs.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

src/resolution/frameworks/index.ts

@@ -13,6 +13,7 @@ import { nestjsResolver } from './nestjs';
 import { reactResolver } from './react';
 import { svelteResolver } from './svelte';
 import { vueResolver } from './vue';
+import { astroResolver } from './astro';
 import { djangoResolver, flaskResolver, fastapiResolver } from './python';
 import { railsResolver } from './ruby';
 import { springResolver } from './java';
@@ -39,6 +40,7 @@ const FRAMEWORK_RESOLVERS: FrameworkResolver[] = [
   reactResolver,
   svelteResolver,
   vueResolver,
+  astroResolver,
   // Python
   djangoResolver,
   flaskResolver,
@@ -128,6 +130,7 @@ export { nestjsResolver } from './nestjs';
 export { reactResolver } from './react';
 export { svelteResolver } from './svelte';
 export { vueResolver } from './vue';
+export { astroResolver } from './astro';
 export { djangoResolver, flaskResolver, fastapiResolver } from './python';
 export { railsResolver } from './ruby';
 export { springResolver } from './java';