Module cohesion (community) was a coarse directory-based rollup with no
effect on retrieval or relation lookup (edges + ref annotations already
cover those), and it was the weakest-value feature per its cost. Remove:

- internal/analysis/community and the CommunityBuilder DI/interface.
- The community rebuild steps in build_or_update_graph and run_postprocess.
- The list_communities, get_community, and get_architecture_overview MCP
  tools plus their handler_graph handlers and response types.
- The community entries in get_minimal_context's tool suggestions.

run_postprocess keeps communities_count (always 0) for wire compatibility.
MCP tools: 31 -> 28. Full suite green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

The project's purpose is annotation + graph + search for preserving code
context, not code-quality metrics. The large-function, dead-code, coupling,
and coverage analyzers were off-purpose, so drop them end to end:

- delete internal/analysis/{largefunc,deadcode,coupling,coverage}
- remove find_large_functions and find_dead_code MCP tools (28 -> 26)
- drop the architecture_map prompt (community + coupling) and the
  coverage/dead-code/large-function sections from review_changes,
  onboard_developer, and pre_merge_check
- remove the 4 analyzer Deps fields, DI wiring, and interface assertions
- prune dead request DTOs and decoders in handler_analysis_io.go
- update tests and guide/skill docs to match the reduced tool set

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>