docs: add typed contribution templates and tighten contributor guidelines (#1673)

Overhaul CONTRIBUTING.md and all GitHub issue/PR templates to enforce a
structured, approval-gated contribution process that cuts down on drive-by
feature submissions.

Changes:
- CONTRIBUTING.md: add Types of Contributions section defining Fix,
  Enhancement, and Feature with escalating requirements and explicit
  rejection criteria; add Issue-First Rule section making clear that
  enhancements require approved-enhancement and features require
  approved-feature label before any code is written; backport gsd-2
  testing standards (t.after() per-test cleanup, array join() fixture
  pattern, Node 24 as primary CI target, test requirements by change type,
  reviewer standards)

- .github/ISSUE_TEMPLATE/enhancement.yml: new template requiring current
  vs. proposed behavior, reason/benefit narrative, full scope of changes,
  and breaking changes assessment; cannot be clicked through

- .github/ISSUE_TEMPLATE/feature_request.yml: full rewrite requiring solo-
  developer problem statement, what is being added, full file-level scope,
  user stories, acceptance criteria, maintenance burden assessment, and
  alternatives considered; incomplete specs are closed, not revised

- .github/pull_request_template.md: converted from general template to a
  routing page directing contributors to the correct typed template;
  using the default template for a feature or enhancement is a rejection
  reason

- .github/PULL_REQUEST_TEMPLATE/fix.md: new typed template requiring
  confirmed-bug label on linked issue and regression test confirmation

- .github/PULL_REQUEST_TEMPLATE/enhancement.md: new typed template with
  hard gate on approved-enhancement label and scope confirmation section

- .github/PULL_REQUEST_TEMPLATE/feature.md: new typed template requiring
  file inventory, spec compliance checklist from the issue, and scope
  confirmation that nothing beyond the approved spec was added

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

.github/pull_request_template.md

@@ -1,59 +1,38 @@
-## Linked Issue
+## ⚠️ Wrong template — please use the correct one for your PR type
 
-> **Required.** PRs without a linked issue are closed without review.
-> Open an issue first if one doesn't exist: https://github.com/gsd-build/get-shit-done/issues/new/choose
+Every PR must use a typed template. Using this default template is a reason for rejection.
 
-Closes #
+Select the template that matches your PR:
 
-## What
+| PR Type | When to use | Template link |
+|---------|-------------|---------------|
+| **Fix** | Correcting a bug, crash, or behavior that doesn't match documentation | [Use fix template](?template=PULL_REQUEST_TEMPLATE/fix.md) |
+| **Enhancement** | Improving an existing feature — better output, expanded edge cases, performance | [Use enhancement template](?template=PULL_REQUEST_TEMPLATE/enhancement.md) |
+| **Feature** | Adding something new — new command, workflow, concept, or integration | [Use feature template](?template=PULL_REQUEST_TEMPLATE/feature.md) |
 
-<!-- One sentence: what does this PR do? -->
+---
 
-## Why
+### Not sure which type applies?
 
-<!-- One sentence: why is this change needed? -->
+- If it **corrects broken behavior** → Fix
+- If it **improves existing behavior** without adding new commands or concepts → Enhancement
+- If it **adds something that doesn't exist today** → Feature
+- If you are not sure → open a [Discussion](https://github.com/gsd-build/get-shit-done/discussions) first
 
-## How
+---
 
-<!-- Brief description of the approach taken. Skip for trivial changes. -->
+### Reminder: Issues must be approved before PRs
 
-## Testing
+For **enhancements**: the linked issue must have the `approved-enhancement` label before you open this PR.
 
-### Platforms tested
+For **features**: the linked issue must have the `approved-feature` label before you open this PR.
 
-- [ ] macOS
-- [ ] Windows (including backslash path handling)
-- [ ] Linux
+PRs that arrive without a labeled, approved issue are closed without review.
 
-### Runtimes tested
+See [CONTRIBUTING.md](../CONTRIBUTING.md) for the full process.
 
-- [ ] Claude Code
-- [ ] Gemini CLI
-- [ ] OpenCode
-- [ ] Codex
-- [ ] Copilot
-- [ ] N/A (not runtime-specific)
+---
 
-### Test details
-
-<!-- How did you verify this works? Manual steps, automated tests, etc. -->
-
-## Checklist
-
-- [ ] Issue linked above (`Closes #NNN`) — **PR will be auto-closed if missing**
-- [ ] Follows GSD style (no enterprise patterns, no filler)
-- [ ] Updates CHANGELOG.md for user-facing changes
-- [ ] No unnecessary dependencies added
-- [ ] Works on Windows (backslash paths tested)
-- [ ] Templates/references updated if behavior changed
-- [ ] Existing tests pass (`npm test`)
-
-## Breaking Changes
-
-<!-- List any breaking changes, or write "None" -->
-
-None
-
-## Screenshots / recordings
-
-<!-- If this is a visual change, add before/after screenshots. Delete this section if not applicable. -->
+<!-- If you believe your PR genuinely does not fit any of the above categories (e.g., CI/tooling changes,
+     dependency updates, or doc-only fixes with no linked issue), delete this file and describe your PR below.
+     Add a note explaining why none of the typed templates apply. -->