Drop .skill zip artifacts and release workflow

The .skill format is a Claude-specific construct. With `npx skills add`
as the primary install path (supporting 20+ agents), the zip artifacts
are redundant. Removed the release workflow that built them and cleaned
up references in CONTRIBUTING, SUPPORT, and the PR template.

Tagged releases with changelogs remain — they just no longer carry
build artifacts.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: jdevalk

.github/PULL_REQUEST_TEMPLATE.md

@@ -12,7 +12,7 @@
 ## Release Impact
 
 - [ ] No release impact
-- [ ] Existing `.skill` package changes
+- [ ] Existing skill content changes
 - [ ] New or renamed skill directory
 
 ## Notes

.github/workflows/release.yml

@@ -48,4 +48,4 @@ If you do not have those tools installed locally, rely on GitHub Actions for fin
 
 ## Releases
 
-Releases are built from this repository's workflow configuration and publish `.skill` archives for each top-level skill directory. Do not rename skill directories casually because release filenames and validation assume stable names.
+Releases are tagged from `main` and documented with changelogs. Skills are distributed via `npx skills add jdevalk/skills` — no build artifacts. Do not rename skill directories casually because the skills CLI, `versions.json`, and validation assume stable names.

CONTRIBUTING.md

@@ -7,7 +7,7 @@ Use GitHub issues for questions about:
 - choosing the right skill
 - improving wording or examples
 - missing documentation
-- packaging or installation problems with published `.skill` files
+- installation problems via `npx skills add`
 
 ## Bugs