fix: harden Buddy session format support

[jazzyalex]

Summary

• harden CodeBuddy/WorkBuddy JSONL parsing for camelCase/snake_case IDs, nested message content, nested tool calls/results, timestamp units, model/cwd variants, and unknown meta-event preservation
• add source-controlled CodeBuddy and WorkBuddy stage0 compatibility fixtures plus parser/search/discovery coverage
• keep Buddy out of FTS-backed indexing and prevent large unindexed Buddy logs from being full-parsed unless deep scan is enabled

Validation

• Baseline before hardening: focused PR tests passed, 33 tests / 0 failures
• Baseline before hardening: Debug build passed
• git diff --check
• fixture scan: rg -n "/Users/|@|token|secret|cookie|authorization|api[_-]?key|BEGIN PRIVATE" Resources/Fixtures/stage0/agents/codebuddy Resources/Fixtures/stage0/agents/workbuddy returned no matches
• Focused Buddy/search/provider/stage0 suite after hardening: 56 tests / 0 failures
• ./scripts/xcode_test_stable.sh: 734 tests, 3 skipped, 0 failures
• Debug build: ** BUILD SUCCEEDED **
• Post-rebase focused Buddy/search/provider/stage0 suite: 56 tests / 0 failures

Compatibility note

I could not capture fresh local vendor sessions on this machine: codebuddy is not installed and neither ~/.codebuddy nor ~/.workbuddy exists. The fixtures in this PR are source-controlled compatibility fixtures with representative Buddy schema drift, not authenticated redacted exports from a real local CodeBuddy/WorkBuddy run.

Before release or public marketing, @tanguofu or another Buddy user should confirm this branch against real local CodeBuddy and WorkBuddy session files, or provide redacted examples for fixture replacement/expansion. Public wording should stay limited to local transcript browsing/search until that verification lands.

Follow-up to #37.

[jazzyalex]

Closing this follow-up as no longer planned.

After maintainer review, CodeBuddy and WorkBuddy support has been reverted from main in e723fdd. The project will not support these providers for now because CodeBuddy cannot be reliably verified from my US region and WorkBuddy is currently Chinese-only, which makes maintenance and QA impractical.

Thanks for the earlier validation work; I am keeping provider support limited to tools that can be verified and maintained locally.