chore: add CLAUDE.md agent guidance (+ AGENTS.md/GEMINI.md symlinks)

[rahlk]

Adds CLAUDE.md agent guidance for codeanalyzer-go, mirroring the setup in the sibling analyzers (codeanalyzer-python/-java/-typescript).

Base branch note: targeted at feat/initial-implementation rather than main, because that's where the actual code lives (main is currently an empty stub). This keeps the guidance next to the code it documents.

• What this project is — the CLDK Go backend (go/packages + go/types resolver call graph), with an explicit Status section that's honest about what's implemented vs. stubbed (CodeQL, msgpack, framework entrypoint finders, Neo4j are all not-yet-implemented).
• Architecture — the Analyzer.Analyze() pipeline in internal/core, phase by phase.
• Directory map, Commands (go build/test/vet), working conventions, and the teaching-loop philosophy.

Also symlinks AGENTS.md and GEMINI.md → CLAUDE.md (force-added past the global AGENTS.md gitignore).

Closes #1