Add sssf skill, installable via the skills CLI

Port the sssf skill from ~/.agents/skills/sssf into this repo so it can be
distributed and installed with the skills CLI (skills add INDigitalStudio/skills
--skill sssf).

- Copy the skill (SKILL.md, cookbooks, references, scripts, templates, and the
  visualizer app source) into sssf/.
- Gitignore build/runtime artifacts: the visualizer's node_modules/ and dist/,
  Python bytecode, and the machine-specific repos.json.
- Make the skill location-independent: install.py now stamps the skill's real
  path into the stamped justfile's skill_dir (replacing the hardcoded
  ~/.agents/skills/sssf), so 'just obs' finds the visualizer wherever the CLI
  installed the skill.
- Update cookbooks to use <skill>/scripts/... instead of the hardcoded path,
  and document the skills CLI install command.
- Update the repo README with install instructions.

sssf/apps/visualizer/tsconfig.json

@@ -0,0 +1,30 @@
+{
+  "compilerOptions": {
+    "target": "ESNext",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "lib": ["ESNext", "DOM", "DOM.Iterable"],
+    "types": ["bun", "vite/client"],
+
+    "strict": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "noFallthroughCasesInSwitch": true,
+    "verbatimModuleSyntax": true,
+    "isolatedModules": true,
+    "skipLibCheck": true,
+    "resolveJsonModule": true,
+    "allowImportingTsExtensions": true,
+    "esModuleInterop": true,
+    "jsx": "preserve",
+    "jsxImportSource": "vue",
+    "noEmit": true,
+
+    "baseUrl": ".",
+    "paths": {
+      "@/*": ["./src/*"],
+      "@shared/*": ["./shared/*"]
+    }
+  },
+  "include": ["shared/**/*.ts", "server/**/*.ts", "src/**/*.ts", "src/**/*.vue", "vite.config.ts"]
+}