fix(extraction): index Vue <template> component usages (#629 follow-up) (#659)

Vue's extractor parsed only the <script> block, so a component used solely
in another component's <template> (`<MyButton />`) produced no reference —
and thus showed a false 0 callers, even after the barrel-resolution fix in
PR #657. This is the Vue analogue of Svelte's extractTemplateComponents.

extractTemplateComponents() now scans the template (everything outside the
<script>/<style> blocks, which also handles nested <template> tags for
v-if/slots) for component tags:
- PascalCase tags (`<MyButton/>`) — captured as-is.
- kebab-case tags (`<my-button/>`) — converted to PascalCase so they match
  the imported component's name. Safe: an unmatched name creates no edge
  during resolution, so native custom elements just don't resolve.
- Native HTML elements (lowercase, no hyphen) and Vue built-ins
  (Transition, KeepAlive, …) are skipped.

Adds no nodes — only `references` — so node counts stay stable. With this
plus #657, a Vue component re-exported through a barrel and used only in a
template now resolves end-to-end (callers/impact/callees).

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -27,6 +27,7 @@ and adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 - Asking what a symbol impacts no longer drags in every unrelated sibling method of its class — impact now follows real dependencies instead of the structural "contains" relationship, keeping the result focused on what actually depends on the symbol. (#536)
 - CodeGraph's MCP server now answers an agent's `resources/list` and `prompts/list` probes with an empty list instead of an error, clearing the `-32601` messages some clients (opencode, Codex) logged on connect. (#621)
 - Svelte and Vue components used through a barrel file — `export { default as Button } from './Button.svelte'` re-exported from an `index.ts` and imported elsewhere — are no longer falsely reported as having **0 callers**. CodeGraph now follows the default re-export all the way to the component and resolves the imports that `.svelte` / `.vue` files themselves use, so `codegraph_callers` and `codegraph_impact` see every place a component is used. This also covers components imported from another package in a workspace/monorepo (`@scope/ui/widgets`) and bare directory imports (`import { x } from './'`). Previously a live component consumed only through a barrel looked like dead code. Thanks @nakisen. (#629)
+- Components used in a Vue Single-File Component's `<template>` — `<MyButton />`, or the kebab-case `<my-button />` — are now indexed as usages, so `codegraph_callers` and `codegraph_impact` include components that appear only in another component's markup (including through a barrel re-export). Previously only a Vue component's `<script>` block was analyzed, so template-only usages were invisible. (#629)
 
 ## [0.9.9] - 2026-06-02