Consolidate documentation: move maintainer docs to docs/, remove redundant files

- Move RELEASING.md and LINTING.md to docs/ (maintainer-only content)
- Delete WORKFLOW.md (agent workflow content belongs in AGENTS.md)
- Delete TEXT_FORMATS.md (technical details belong in ADVANCED.md)
- Update all cross-references to point to new locations
- Keep CLAUDE.md (required by Claude Code)

Reduces root-level docs from 20 to 16 files with clearer organization.

Amp-Thread-ID: https://ampcode.com/threads/T-fe1db4f3-16c6-4a79-8887-c7f4c1f11c43
Co-authored-by: Amp <amp@ampcode.com>

LABELS.md

@@ -527,5 +527,5 @@ bd import -i .beads/issues.jsonl
 
 - [README.md](README.md) - Main documentation
 - [AGENTS.md](AGENTS.md) - AI agent integration guide
-- [WORKFLOW.md](WORKFLOW.md) - Team workflow patterns
-- [TEXT_FORMATS.md](TEXT_FORMATS.md) - JSONL format details
+- [AGENTS.md](AGENTS.md) - Team workflow patterns
+- [ADVANCED.md](ADVANCED.md) - JSONL format details