refactor: move all shell scripts to /sh directory (#1843)

Reorganizes the project so all shell scripts live under a dedicated
/sh directory, enabling the OpenRouter rewrite URL to point at /sh/
instead of the repository root.

Moves:
- cli/install.sh → sh/cli/install.sh
- shared/*.sh → sh/shared/*.sh
- {cloud}/{agent}.sh → sh/{cloud}/{agent}.sh (48 scripts)
- {cloud}/README.md → sh/{cloud}/README.md
- e2e/*.sh → sh/e2e/*.sh
- test/macos-compat.sh → sh/test/macos-compat.sh
- test/fixtures/**/*.sh → sh/test/fixtures/**/*.sh

Updates all references:
- RAW_BASE path construction in commands.ts, update-check.ts
- GitHub auth URL in agent-setup.ts
- Self-referencing URLs in install.sh, github-auth.sh
- CI workflow paths in lint.yml, cli-release.yml
- Test file paths in install-script-validation, manifest-integrity
- Documentation in README.md, cli/README.md, CLAUDE.md
- QA scripts in .claude/skills/

Co-authored-by: lab <6723574+louisgv@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.github/workflows/cli-release.yml

@@ -79,7 +79,7 @@ jobs:
               --title "${name} bundle v${{ steps.version.outputs.version }}" \
               --notes "Pre-built ${name} cloud provider bundle.
 
-          Downloaded by \`${name}/*.sh\` shims for \`bash <(curl ...)\` execution.
+          Downloaded by \`sh/${name}/*.sh\` shims for \`bash <(curl ...)\` execution.
 
           **Built:** $(date -u +%Y-%m-%dT%H:%M:%SZ)" \
               --prerelease \