feat(context): token-efficient symbols overview fast-path (closes #254)

[Wolfvin]

Summary

• Adds `context --check overview` — queries `graph_nodes` directly (no re-parse, no LSP) and returns compact per-file symbol map (name + kind + line)
• Workspace-wide in 1 call vs outline --all paginating 20 files/call
• Supports `--file` filter for per-file mode and `--max-files` cap (default 200)

Patch Peta

• `scripts/commands/symbols_overview.py` (new) — sqlite3 query on graph_nodes, groups by file, filters noise kinds
• `scripts/commands/context.py` — registered `overview` in `_CHECKS`, namespace branch, epilog updated
• `tests/test_command_registry.py` — symbols_overview added to allowlist
• `tests/test_symbols_overview.py` (new) — 6 tests
• `docs/design/0254-symbols-overview.md` (new)

Testing

• 6 unit tests: no-registry graceful degradation, grouping, file filter, noise exclusion, truncation, no-reparse invariant
• End-to-end verified: `codelens context .. --check overview` → 200 files, 2054 symbols
• Per-file: 1100 chars vs outline 1600 chars (31% smaller); workspace: 1 call covers 200 files

Closes #254

[chatgpt-codex-connector]

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[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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