Fix concurrent session tag updates targeting the wrong tag

[blast-hardcheese]

Summary

• Require an explicit tag name for MCP and CLI update, segment, pause, and end actions. Concurrent sessions in one project can no longer select each other's tags through the most recently updated active tag.
• Update agent guidance and CLI examples to pass the tag name.
• Add regression coverage for unnamed actions with one and two active tags, plus explicit-name end with a more recently updated peer.

Verification

• wander-serialized-test -- env PYTHONPATH=/Users/dstewart/Projects/kindex/fork-session-bugfix/src /Users/dstewart/Projects/kindex/main/.venv/bin/python -m pytest tests/test_mcp.py tests/test_sessions.py -q — 150 passed.
• git diff --check — clean.

The full test suite will run in CI.

[adaptcom]

Confidence Score: 4/5

Summary

Requires explicit tags to prevent cross-session mutations; 2,913 tests pass. Remaining risks are misleading CLI exit codes and stale agent instructions.

Important Files Changed

File	Overview
README.md	Adds explicit tag names to lifecycle examples
docs/mcp-agent-guide.md	Documents mandatory tag names
src/kindex/cli.py	Rejects unnamed mutations but exits successfully
src/kindex/mcp_server.py	Rejects missing or blank tag names
tests/test_mcp.py	Covers unnamed mutation refusal and explicit-name isolation
tests/test_sessions.py	Tests unnamed CLI rejection without asserting failure exit status

Findings

• Update CLAUDE.md:81 and AGENTS.md:81 to include tag names; their update, segment, and end examples now always fail.

↻ Re-run review · View in Adapt

[adaptcom]

Rejected unnamed commands exit 0, so scripts treat lifecycle no-ops as successful; exit nonzero and assert failure status in the new tests.