refactor(scrape): Remove vestigial code.symbol dual-writes from language processors

[nicabarnimble]

Summary

Remove redundant add_symbol() calls for entities that already have richer fact types. This is Phase 2 cleanup following the FTS5 deduplication fix (commit ef6f59c).

Background

The scrape pipeline has vestigial code from an abandoned architecture (Aug 2025):

• Original design (b7c1ddf2): code_search table for text search alongside code_fingerprints for fingerprint similarity
• Current state: code_search is NEVER QUERIED, but language processors still write to it via dual add_symbol() + add_function() calls

The FTS5 fix filters these at query time, but the writes still happen, wasting storage and cycles.

Current Behavior

Every function gets written 4 times per scrape:

1. code.function event → eventlog
2. function_facts table → materialized view
3. code.symbol event → eventlog (REDUNDANT)
4. code_search table → materialized view (NEVER QUERIED)

Proposed Changes

Phase 2a: Remove symbol writes for functions

• Files: src/commands/scrape/code/languages/*.rs (~20 sites)
• Remove data.add_symbol() calls that follow data.add_function()

Phase 2b: Remove symbol writes for types

• Same files, similar pattern for structs/enums/traits

Phase 2c: Remove dead code

• Remove code_search table from schema (src/commands/scrape/code/database.rs)
• Remove insert_symbols() writes to code_search
• Consider deprecating code.symbol event type

Affected Files

File	Sites
rust.rs	~3 (function + struct + enum)
go.rs	~3
python.rs	~3
typescript.rs	~4
javascript.rs	~3
c.rs	~3
cpp.rs	~4
cairo.rs	~2
solidity.rs	~4

Validation

• Run patina scrape - should complete without errors
• Run patina bench retrieval - MRR should not regress
• Verify code_fts has no code.symbol entries (redundant check after Phase 1)
• Storage reduction: eventlog should shrink ~40%

References

• Spec: layer/surface/build/spec-fts-deduplication.md
• Session: 20251222-191614 (git archaeology)
• Phase 1 fix: ef6f59c