refactor: delete sync.sh, dev workflow moves to npx skills add . -g -y + native installers

Every job sync.sh did has a better replacement:

- Per-harness skill dirs (~/.claude/skills, ~/.codex/skills, ~/.agents/skills):
  `npx skills add . -g -y` writes to every detected harness's home dir and
  uses symlinks by default. Edits propagate live — no re-deploy step.
- Hermes (~/.hermes/skills/research/last30days):
  `hermes skills install mvanhorn/last30days-skill --force` pulls from
  GitHub and handles the deploy itself. The script wrapping was redundant.
- OpenClaw variant: `clawhub install last30days-official` is what users
  already run per the README; the maintainer doesn't need a separate
  variant-deploy step in the public repo's scripts.
- Claude marketplace cache (~/.claude/plugins/cache/...): this was a
  "test against the official install path" hack we shouldn't have been
  recommending. With PR #400's resolver collapse, STEP 0 no longer
  enforces the cache as the only valid SKILL.md location. Just install
  the skill normally via `npx skills` or the marketplace.

Cleanup:

- DELETE skills/last30days/scripts/sync.sh
- tests/test_version_consistency.py — drop test_sync_cache_path_uses_skill_version
- CLAUDE.md — replace the sync.sh command + rule with `npx skills add . -g -y`
- HERMES_SETUP.md — Installation now uses `hermes skills install --force`;
  developer-alternative section shows the symlink pattern for live editing
- render.py — _skill_version docstring no longer attributes the
  ".claude-plugin absent" case to sync.sh; explains it via per-harness
  install paths in general
- .github/PULL_REQUEST_TEMPLATE.md — drop the "Ran bash scripts/sync.sh"
  checklist item

CHANGELOG and historical docs (release notes, plan files) keep their
existing sync.sh mentions as accurate history.

HERMES_SETUP.md

@@ -10,28 +10,20 @@ This guide covers installing last30days on Hermes AI Agent.
 
 ## Installation
 
-### Option 1: Via sync.sh (Recommended)
-
 ```bash
-# Clone the repo
-git clone https://github.com/mvanhorn/last30days-skill.git
-cd last30days-skill
-
-# Run the sync script
-bash skills/last30days/scripts/sync.sh
+hermes skills install mvanhorn/last30days-skill --force
 ```
 
-This will auto-detect Hermes and deploy to `~/.hermes/skills/research/last30days/`
+This pulls the latest release from GitHub and deploys to `~/.hermes/skills/research/last30days/`. `--force` reinstalls over any existing copy.
 
-### Option 2: Manual Copy
+### Developer / live-edit alternative
+
+If you're hacking on the skill locally and want edits to propagate to Hermes without re-installing, symlink your working tree:
 
 ```bash
-# Create directory
-mkdir -p ~/.hermes/skills/research/last30days
-
-# Copy files
-cp skills/last30days/SKILL.md ~/.hermes/skills/research/last30days/
-cp -r skills/last30days/scripts ~/.hermes/skills/research/last30days/
+git clone https://github.com/mvanhorn/last30days-skill.git
+mkdir -p ~/.hermes/skills/research
+ln -s "$(pwd)/last30days-skill/skills/last30days" ~/.hermes/skills/research/last30days
 ```
 
 ## Usage
@@ -106,14 +98,12 @@ python3.12 scripts/last30days.py --diagnose
 
 ## Updating
 
-To update to the latest version:
-
 ```bash
-cd last30days-skill
-git pull
-bash skills/last30days/scripts/sync.sh
+hermes skills install mvanhorn/last30days-skill --force
 ```
 
+If you symlinked your working tree (developer alternative above), just `git pull` in the repo — edits propagate live, no re-install step.
+
 ## Support
 
 - Original repo: https://github.com/mvanhorn/last30days-skill