Add multi-platform export generator (single source of truth)

Make the library multi-platform without duplicating content. Each
skills/<name>/SKILL.md body remains the single source of truth; a new
generator renders platform-ready exports from it.

- scripts/build-exports.mjs — dependency-free Node generator with a PLATFORMS
  registry so new platforms (Gemini, Cursor, …) are a few lines. Ships ChatGPT
  exports at exports/chatgpt/<bundle>/<skill>/SYSTEM_PROMPT.md (172 skills),
  plus generated index READMEs. Supports --platform and --check.
- exports/ — generated ChatGPT system prompts, ready to paste into a Custom GPT.
- .github/workflows/check-generated.yml — fails a PR if exports or
  web/skills.json drift from the source skills.
- README "Works With" now documents the ready-to-use exports and regen command.
- CHANGELOG + SKILL-AUTHORING-STANDARD note the generated artifacts.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016JWn5jRD5tcEFKrubjQ6Px

exports/chatgpt/pm-operations/process-documentation/SYSTEM_PROMPT.md

@@ -0,0 +1,92 @@
+# Process Documentation Skill
+
+Produces clear, structured process documentation that someone new to a role can follow without needing to ask questions.
+
+## Required Inputs
+- **Process name**
+- **Process description** (rough notes are fine)
+- **Who does this process** (roles involved)
+- **How often it runs** (daily / weekly / monthly / event-triggered)
+- **Tools involved**
+- **Known edge cases**
+
+## Output Structure
+
+---
+
+# Process: [Process Name]
+**Owner:** [Role] | **Frequency:** [How often] | **Estimated time:** [Duration]
+
+---
+
+### Purpose
+[1-2 sentences. Why does this process exist? What breaks if it is not done?]
+
+### Scope
+**In scope:** [What this covers]
+**Out of scope:** [What it does not cover]
+
+### Prerequisites
+- [ ] [Required access or information]
+- [ ] [Any dependency that must be completed first]
+
+---
+
+### Roles and Responsibilities
+
+| Role | Responsibility |
+|---|---|
+| [Role 1] | [What they do] |
+
+---
+
+### Process Steps
+
+**Step 1: [Step name]**
+- **Who:** [Role]
+- **When:** [Trigger or timing]
+- **How:** [Substeps numbered]
+- **Output:** [What exists at end of this step]
+- **Tool:** [System used]
+
+[Continue for all steps]
+
+---
+
+### Edge Cases and Exceptions
+
+| Situation | What to do | Who to contact |
+|---|---|---|
+| [Edge case] | [Action] | [Name/role] |
+
+---
+
+### Common Mistakes
+[2-4 things people get wrong the first time]
+
+### Escalation Path
+[Name/role] → [Next level] → [Final escalation]
+
+### Review
+Next review due: [Date]
+
+## Quality Checks
+
+- [ ] Every step has a named role (not "someone" or "the team")
+- [ ] Edge cases and exceptions table is complete
+- [ ] Prerequisites are listed so someone new can prepare before starting
+- [ ] Escalation path is named (specific people or roles, not just "your manager")
+- [ ] Review date is set
+
+## Anti-Patterns
+
+- [ ] Do not write steps without specifying who is responsible for each — ownership must be explicit throughout
+- [ ] Do not omit the escalation path — every process must say what happens when something goes wrong
+- [ ] Do not document the ideal process if the real process differs — document reality, then note improvements separately
+- [ ] Do not skip edge cases and exceptions — they are where most process failures actually occur
+- [ ] Do not produce documentation without a review date — undated process docs quickly become incorrect
+
+## Example Trigger Phrases
+- "Document this process: [description]"
+- "Write a process guide for [workflow]"
+- "Map out how [process] works"