Auto-launch adopted tasks in herdr

[gering]

Summary

• Extend /adopt so that, inside a herdr session, it opens the task's tab and starts the chosen worker after creating the worktree — exactly like /kickoff.
• Outside herdr, /adopt prints the manual launch block unchanged (now registry-driven, so it honors the selected worker).
• Reuses the shared herdr-launch.sh helper — no launch logic duplicated; the intricate result-branching stays a single source in /kickoff.

Changes

• adopt/SKILL.md: new [agent-selector] argument; step 12 (worker selection, deferring to kickoff step 12 for picker/announce rules); step 13 (herdr gate → herdr-launch.sh launch with the selector, branching via kickoff step 13a; else a registry-driven manual block).
• Label derives from the resolved task name, so it stays sensible when /adopt keeps the original branch name; templates show the adopted branch, not an assumed task/<name>; worktree path built from the main-repo path captured in step 1 (cwd-safety).
• READMEs: herdr section + root README note /adopt auto-launches too; Adopting section lists the selector flags.
• Knowledge: herdr-kickoff-automation extended with the adopt auto-launch and its reference-not-duplicate design decision.
• Version: work-system 1.9.2 → 1.9.3 (plugin.json + marketplace.json).

Readiness

• ✅ READMEs updated (root + work-system)
• ✅ Version bumped to 1.9.3 (both files in sync)
• ➖ Changelog N/A (repo has none)
• ✅ Knowledge entry updated
• ✅ check-structure.py: 0 errors
• ➖ Lint / Build N/A (markdown-only plugin repo)

Test plan

• Inside herdr: /adopt <branch> opens a background tab at the worktree running the chosen worker
• Inside herdr with --pick/--sol: worker selection routes through the registry and the manual block/tab reflects it
• Outside herdr: /adopt <branch> prints the registry-driven manual launch block, worktree created unchanged
• /adopt that keeps the original branch name → tab label + templates still use the resolved task name / adopted branch

🤖 Generated with Claude Code