feat: add first-pass Svelte language support

[justrach]

Summary

• add .svelte language detection and a Svelte parser wrapper that only extracts symbols from <script> blocks
• surface Svelte in language styling and special-entrypoint ranking
• fix telemetry language-name ordering so existing php and ruby bits stay aligned while adding svelte
• add targeted tests for Svelte parsing, inline <script> handling, detectLanguage coverage, and telemetry output

Verification

• zig test src/tests.zig --test-filter 'Svelte:'
• zig test src/tests.zig --test-filter 'issue-59: telemetry writes session, tool, and codebase stats ndjson'
• zig test src/tests.zig --test-filter 'detectLanguage:'
• zig test src/tests.zig --test-filter 'isCommentOrBlank: detects language-specific comments'

Notes

• zig build test still fails on origin/main because the pre-existing issue-150 help-output tests are red in a clean baseline worktree as well.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Keep Language enum values stable across snapshot versions

Adding svelte before unknown changes the numeric value of Language.unknown, but snapshot serialization stores @intFromEnum(outline.language) and deserializes it with intToEnum (src/snapshot.zig), and the loader does not gate on a bumped format version. That means snapshots produced by the previous build will decode old unknown entries as svelte after this change, causing incorrect language metadata on warm restore. Please preserve ordinal stability (explicit enum values or append-only ordering) or bump/migrate snapshot format when enum layout changes.

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