feat: add _WRITING skill stub (rewrite + detect modes)

Releases/v5.0.0/.claude/skills/_WRITING/SKILL.md

@@ -0,0 +1,65 @@
+---
+name: _WRITING
+description: "Two-mode AI writing pattern tool that uses AI_WRITING_PATTERNS.md as its rule source. rewrite mode: strips AI-isms from a given text (P0 credibility killers removed silently, P1/P2 surfaced as candidates with brief reason). detect mode: audits text and returns a scored list of pattern hits (P-level, pattern, excerpt, suggested fix). Invoke as: /writing rewrite <text or @file> or /writing detect <text or @file>. User-instantiated skill — extend with patterns from your own AI_WRITING_PATTERNS.md P2 section. USE WHEN: polish text for AI tells, rewrite AI-generated prose, detect AI writing patterns, scrub AI-isms, check writing for AI smell, writing audit, writing cleanup."
+---
+
+# _WRITING — AI Writing Pattern Cleaner
+
+Reads `~/.claude/PAI/USER/AI_WRITING_PATTERNS.md` as its rule source and operates in two modes.
+
+## Modes
+
+### `rewrite` — strip AI patterns from text
+
+**Input**: raw text (inline or via `@file`)
+
+**Workflow**:
+1. Load patterns from `AI_WRITING_PATTERNS.md` (P0, P1, P2 sections).
+2. Apply P0 (credibility killers) silently — remove without comment.
+3. For P1/P2 hits, propose the rewrite and state the pattern triggered.
+4. Output the cleaned text followed by a brief change log.
+
+**Output format**:
+```
+[Rewritten text]
+
+---
+Changes made:
+- Removed "Let me know if..." (P0)
+- Replaced "Here's the thing..." → "[rewritten phrase]" (P1)
+```
+
+### `detect` — audit text for AI tells
+
+**Input**: raw text (inline or via `@file`)
+
+**Workflow**:
+1. Load patterns from `AI_WRITING_PATTERNS.md`.
+2. Scan the text for each pattern by P-level.
+3. Return a scored hit list.
+
+**Output format**:
+```
+Pattern audit — 3 hits
+
+P0  "Let me know if you need anything else."  → Remove entirely
+P1  "Here's the thing:"                       → Cut or recast
+P2  [user-defined pattern]                    → [user-defined guidance]
+
+Overall AI-smell score: HIGH / MEDIUM / LOW / CLEAN
+```
+
+## Usage
+
+```
+/writing rewrite <text>
+/writing rewrite @path/to/file.md
+/writing detect <text>
+/writing detect @path/to/file.md
+```
+
+## Customization
+
+Add your own patterns to the **P2 section** of `~/.claude/PAI/USER/AI_WRITING_PATTERNS.md`. This skill reads that file on every invocation, so changes take effect immediately without restarting.
+
+The `_` prefix means this skill is user-instantiated — it ships as a starting point. Extend the P2 section with patterns specific to your voice and writing style.