refactor(plugin)!: ship as a Claude Code plugin, one dir link per harness

Skills move to skills/<name>/SKILL.md and the repo gains both manifests, so
it is now a marketplace hosting exactly one plugin whose root is the repo
root (source: "."). Claude Code installs it from git; no symlinks involved.

Why: install.sh wired the library into every consuming repo as an ABSOLUTE
symlink to $CHECKOUT_DIR. The checkout moved three times, most recently when
local-dev@1966d5a dropped the embedded .skills/ copy, and nothing migrated
the links — 243 dangling links across 12 repos, hidden from git by the
**/.claude/skills/ ignore rule. Worse, ~/dev spans two path roots
(/Users/mathias on the iCloud-shared Macs, /home/mathias on koala), so an
absolute link stored there is broken on one side by construction. Re-running
the installer cannot fix that; only removing the mechanism can.

install.sh keeps the harnesses with no plugin system and drops from 42 links
per harness to one directory link, via the convergent ~/.agents/skills
convention that Pi and OpenCode both read:

  ~/.agents/skills          -> $CHECKOUT_DIR/skills
  ~/.config/crush/skills    -> ~/.agents/skills
  ~/.config/opencode/skills -> ~/.agents/skills

wire_claude_repo is deleted outright rather than gated behind a flag — on a
mixed-root fleet it cannot be made correct. Antigravity and Vibe targets go
too; both unused. CHECKOUT_DIR keeps its host-local default deliberately:
pointing it into ~/dev would put a git working tree inside iCloud with two
concurrent writers.

Taskfile drops five near-identical wiring loops (they had already drifted)
and delegates to install.sh. `task check` gains frontmatter validation, a
stray-root-entry gate, and manifest/tag version parity — the loose
secret-hygiene.md sat unloadable for months because nothing checked layout.

Verified: claude plugin validate . passes clean; a probe skill loaded as
skills:zzprobe through --plugin-dir; task check green at 42 skills.

Refs: #23
Bump-Type: minor

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BeAp5LTscnz2W7Ubt4eJ6m

skills/superpowers-subagent-driven-development/implementer-prompt.md

@@ -0,0 +1,113 @@
+# Implementer Subagent Prompt Template
+
+Use this template when dispatching an implementer subagent.
+
+```
+Task tool (general-purpose):
+  description: "Implement Task N: [task name]"
+  prompt: |
+    You are implementing Task N: [task name]
+
+    ## Task Description
+
+    [FULL TEXT of task from plan - paste it here, don't make subagent read file]
+
+    ## Context
+
+    [Scene-setting: where this fits, dependencies, architectural context]
+
+    ## Before You Begin
+
+    If you have questions about:
+    - The requirements or acceptance criteria
+    - The approach or implementation strategy
+    - Dependencies or assumptions
+    - Anything unclear in the task description
+
+    **Ask them now.** Raise any concerns before starting work.
+
+    ## Your Job
+
+    Once you're clear on requirements:
+    1. Implement exactly what the task specifies
+    2. Write tests (following TDD if task says to)
+    3. Verify implementation works
+    4. Commit your work
+    5. Self-review (see below)
+    6. Report back
+
+    Work from: [directory]
+
+    **While you work:** If you encounter something unexpected or unclear, **ask questions**.
+    It's always OK to pause and clarify. Don't guess or make assumptions.
+
+    ## Code Organization
+
+    You reason best about code you can hold in context at once, and your edits are more
+    reliable when files are focused. Keep this in mind:
+    - Follow the file structure defined in the plan
+    - Each file should have one clear responsibility with a well-defined interface
+    - If a file you're creating is growing beyond the plan's intent, stop and report
+      it as DONE_WITH_CONCERNS — don't split files on your own without plan guidance
+    - If an existing file you're modifying is already large or tangled, work carefully
+      and note it as a concern in your report
+    - In existing codebases, follow established patterns. Improve code you're touching
+      the way a good developer would, but don't restructure things outside your task.
+
+    ## When You're in Over Your Head
+
+    It is always OK to stop and say "this is too hard for me." Bad work is worse than
+    no work. You will not be penalized for escalating.
+
+    **STOP and escalate when:**
+    - The task requires architectural decisions with multiple valid approaches
+    - You need to understand code beyond what was provided and can't find clarity
+    - You feel uncertain about whether your approach is correct
+    - The task involves restructuring existing code in ways the plan didn't anticipate
+    - You've been reading file after file trying to understand the system without progress
+
+    **How to escalate:** Report back with status BLOCKED or NEEDS_CONTEXT. Describe
+    specifically what you're stuck on, what you've tried, and what kind of help you need.
+    The controller can provide more context, re-dispatch with a more capable model,
+    or break the task into smaller pieces.
+
+    ## Before Reporting Back: Self-Review
+
+    Review your work with fresh eyes. Ask yourself:
+
+    **Completeness:**
+    - Did I fully implement everything in the spec?
+    - Did I miss any requirements?
+    - Are there edge cases I didn't handle?
+
+    **Quality:**
+    - Is this my best work?
+    - Are names clear and accurate (match what things do, not how they work)?
+    - Is the code clean and maintainable?
+
+    **Discipline:**
+    - Did I avoid overbuilding (YAGNI)?
+    - Did I only build what was requested?
+    - Did I follow existing patterns in the codebase?
+
+    **Testing:**
+    - Do tests actually verify behavior (not just mock behavior)?
+    - Did I follow TDD if required?
+    - Are tests comprehensive?
+
+    If you find issues during self-review, fix them now before reporting.
+
+    ## Report Format
+
+    When done, report:
+    - **Status:** DONE | DONE_WITH_CONCERNS | BLOCKED | NEEDS_CONTEXT
+    - What you implemented (or what you attempted, if blocked)
+    - What you tested and test results
+    - Files changed
+    - Self-review findings (if any)
+    - Any issues or concerns
+
+    Use DONE_WITH_CONCERNS if you completed the work but have doubts about correctness.
+    Use BLOCKED if you cannot complete the task. Use NEEDS_CONTEXT if you need
+    information that wasn't provided. Never silently produce work you're unsure about.
+```