fix: support git worktree scoping (#1)

* fix: detect git worktree roots where .git is a file

FindProjectRoot() only checked for .git as a directory, missing git
worktrees where .git is a regular file containing a gitdir pointer.
This caused all worktrees to resolve to the main repo's storage path,
colliding on tasks, sessions, and drain state.

* test: add worktree detection tests for FindProjectRoot

Add three new subtests covering git worktree scenarios:
- finds .git file in current directory (worktree)
- finds .git file in parent directory (worktree)
- worktree and normal repo produce different store paths

* docs: add CLAUDE.md and document git worktree support in README

Add project-level CLAUDE.md with architecture overview, storage design,
and testing conventions. Update README to mention worktree isolation in
the philosophy section and storage format section.

docs: update documentation for autonomous drain model

Update README, plugin rules, and plugin version to reflect:
- session compact command and compaction hook
- drain release --force flag and guard behavior
- 12-hour drain timeout in stop hook
- Updated plugin descriptions (goal contracts, autonomous loop)
- Manual hook config now includes compact SessionStart hook

Bump plugin version to 0.3.0 (new command, new hooks, skill rewrites).

feat: add Claude Code plugin for bits integration

Add a Claude Code plugin with skills, commands, and hooks:
- bits skill for task tracking operations
- bits-plan skill for extracting tasks from conversations
- bits-drain command for working through all tasks
- Session lifecycle hooks for drain mode blocking

Plugin includes governance rules (bits immutability) embedded
in the skill documentation.

feat: prevent drain release when tasks remain incomplete

Add validation check before allowing drain mode to be released.
If active or open tasks still exist, outputs an instructive error
message and exits with code 1, guiding Claude to continue working.

fix: order blocked tasks by dependency chain in list output

Within the blocked group, tasks that block others now appear before
the tasks they block. Previously blocked tasks were sorted only by
priority and creation time, which could show a blocked task before
its blocker.

feat: sort list output with unblocked tasks first

Tasks without blocking dependencies now appear before blocked tasks in
`bits list` output. Within each group, tasks remain sorted by priority
then creation time.

feat: block hook until all tasks are closed

Previously, the hook only blocked when there were active tasks. Now it
blocks on any non-closed tasks (open or active) with context-specific
messages directing users to either continue working or check ready tasks.

feat: add ls alias for list command

fix: resolve symlinks in FindProjectRoot for consistent storage paths

Accessing the same directory via different paths (e.g., /tmp/project vs
/private/tmp/project on macOS) previously created separate storage
locations. Now uses filepath.EvalSymlinks() to canonicalize paths.

chore: remove path filter from quality-check rule

Apply rule globally instead of only to Go files.