SkillCheck validator, Cursor exports, and per-agent installers (#27)

Three more learnings from alirezarezvani/claude-skills, applied:

1. SkillCheck validator (scripts/skillcheck.mjs) — validates every SKILL.md
   against the authoring standard (frontmatter, name/folder match, trigger +
   produces clauses, required headings) plus tier referential integrity.
   Errors fail CI; --strict fails on warnings too. New skillcheck.yml workflow
   and a SkillCheck status badge in the README. Current: 0 errors / 14 advisory
   warnings across 172 skills.

2. Cursor export platform — build-exports.mjs now generates
   exports/cursor/<bundle>/<skill>/<skill>.mdc rule files. The PLATFORMS
   registry now supports per-skill filenames (file as a function).

3. Per-agent installers — scripts/install.sh unifies install for
   claude/hermes/codex/openclaw/cursor (--link, --target, --dry-run, --list).
   Curl-able one-liners codex-install.sh, openclaw-install.sh, and
   cursor-install.sh clone the library and install in a single command.

README documents the one-line installs and Cursor exports; CHANGELOG and the
authoring standard updated.


Claude-Session: https://claude.ai/code/session_016JWn5jRD5tcEFKrubjQ6Px

Co-authored-by: Claude <noreply@anthropic.com>

exports/cursor/pm-discovery/assumption-mapper/assumption-mapper.mdc

@@ -0,0 +1,67 @@
+---
+description: "Extract and risk-rate hidden assumptions in a product brief or PRD. Use when asked to review a product brief for assumptions, audit a PRD for risks, find hidden assumptions, validate product plans, or run an assumption analysis. Produces a prioritised assumption map with confidence and impact scores, recommended validation methods, and critical assumption flags."
+globs:
+alwaysApply: false
+---
+
+# Assumption Mapper Skill
+
+Surface and prioritize the untested assumptions embedded in any product plan before development begins.
+
+## Required Inputs
+
+Ask the user for these if not provided:
+- **Product brief, PRD, or concept description** (even rough notes work)
+- **Stage** (concept / discovery / pre-build / post-launch — affects which assumptions matter most)
+
+## Process
+1. Read the provided brief, PRD, or concept description
+2. Extract assumptions across four categories:
+   - **Desirability** (do users want this?)
+   - **Feasibility** (can we build it?)
+   - **Viability** (will it sustain the business?)
+   - **Usability** (can users actually use it?)
+3. Score each assumption:
+   - Confidence (1-5): How sure are we this is true?
+   - Impact (1-5): How badly does the plan fail if this assumption is wrong?
+   - Priority = Impact − Confidence (higher = test first)
+4. **Validate completeness** — Ensure at least one assumption per category. If a category is empty, re-read the brief looking specifically for that type.
+5. Output a ranked list with recommended validation methods
+
+## Output Structure
+
+### Assumption Map: [Feature/Product Name]
+
+| Assumption | Category | Confidence | Impact | Priority | Validation Method |
+|------------|----------|------------|--------|----------|-------------------|
+| [assumption] | [type] | [1-5] | [1-5] | [score] | [method] |
+
+#### Critical Assumptions (Impact 4+ and Confidence 2 or below)
+[Flagged items with detailed validation recommendations]
+
+#### Top 3 Assumptions to Validate First
+[Detailed recommendations including specific research method, estimated effort, and what the result would change]
+
+## Example (Partial)
+
+Input: *"We're building a self-serve onboarding flow to reduce time-to-value for SMB customers."*
+
+| Assumption | Category | Confidence | Impact | Priority | Validation Method |
+|------------|----------|------------|--------|----------|-------------------|
+| SMB users can complete onboarding without human help | Usability | 2 | 5 | 3 | Unmoderated usability test (n=8) |
+| Faster onboarding correlates with higher retention | Viability | 3 | 4 | 1 | Cohort analysis of current onboarding times vs. 90-day retention |
+| The current onboarding is the primary reason for slow time-to-value | Desirability | 2 | 4 | 2 | User interviews with recent churned SMB accounts |
+
+## Anti-Patterns
+
+- [ ] Do not only surface desirability assumptions — feasibility and viability assumptions are equally likely to kill a product and are often overlooked
+- [ ] Do not assign high confidence to an assumption just because it hasn't been challenged yet — absence of evidence is not evidence
+- [ ] Do not recommend "user interviews" as the validation method for every assumption — some assumptions require quantitative data, competitive analysis, or technical spikes
+- [ ] Do not list assumptions that cannot be tested — every assumption in the map must have a plausible validation method, or it should be flagged as unknowable and treated as a risk
+
+## Quality Checks
+
+- [ ] At least one assumption per category (Desirability, Feasibility, Viability, Usability)
+- [ ] All Impact 4+ / Confidence 2− assumptions flagged as CRITICAL
+- [ ] Each validation method is specific (not just "do research" — name the method and sample size)
+- [ ] Priority scores are consistent (Impact − Confidence, higher = more urgent)