feat: Update command docs to use session_command tags - Add /merge command

[dbpolito]

Ticket

SKIPPED

Description

Updates command documentation to use <session_command> tags instead of <dispatch> tags for navigator-style command delegation. This aligns the docs with the current implementation where session commands are used for same-session dispatch.

Checklist

Documentation

• Updated AGENTS.md to reflect session_command usage
• Verified command authoring guidelines reference correct tags

Commands

• Reviewed navigator delegation patterns in command docs
• Confirmed session_command examples are accurate

Validation

• Verify that all command docs use session_command consistently
• Check that no dispatch tags remain in documentation
• Confirm workflow subsections follow the new pattern

[kompassdev]

★★★★★

This is a well-structured migration PR that cleanly replaces the <dispatch> mechanism with the <session_command> tool approach. The changes are consistent across all command documentation, configuration files, schema, tests, and generated output.

Key observations:

1. Complete migration: All <dispatch> references have been replaced with <session_command> throughout the codebase - command docs, agent docs, AGENTS.md guidelines, compiled output, and tests.

2. Correct tag format: All <session_command> tags use the proper format with both agent and command attributes (e.g., <session_command agent="worker" command="branch">).

3. New implementation: The packages/core/tools/dispatch.ts introduces a clean resolveSessionCommand function that properly expands command templates and resolves agent routing.

4. OpenCode adapter updates: The adapter correctly uses client.session.promptAsync to queue commands instead of the previous expansion approach.

5. Tests validate the changes: All 42 tests pass (5 dispatch tests, 28 commands-config tests, 9 tool-registration tests). The only failing test (pr_load.test.ts) is unrelated to this PR - it's an environmental issue with viewerLogin expectations.

6. Type checking passes: No TypeScript errors.

7. New merge command: The PR also adds a new merge command that follows the established patterns.

Checklist verification:

• ✅ Updated AGENTS.md to reflect session_command usage
• ✅ Verified command authoring guidelines reference correct tags
• ✅ Reviewed navigator delegation patterns in command docs
• ✅ Confirmed session_command examples are accurate
• ✅ Verified all command docs use session_command consistently
• ✅ No dispatch tags remain in documentation
• ✅ Workflow subsections follow the new pattern

No material issues found. The migration is thorough and consistent.