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/templates/adws/adw_plan_build.py

@@ -0,0 +1,55 @@
+#!/usr/bin/env -S uv run
+# /// script
+# dependencies = ["pydantic", "python-dotenv", "pyyaml", "rich"]
+# ///
+"""ADW Plan Build — two-agent chain: planner -> envelope -> builder.
+
+Usage:
+    uv run adws/adw_plan_build.py "<prompt or path/to/prompt.md>" [--config adws/adw_sssf_config/sssf.config.yaml] [--adw-id a1b2c3d4]
+
+Phases: engineer(request) -> planner -> builder -> git(commit)
+"""
+
+import argparse
+import sys
+
+from adw_modules import agents, gates, git_helper, session, utils
+from adw_modules.data_types import AgentCall, BuildOutput, PhaseParams, PlanOutput
+
+REQUIRED_AGENTS = ["planner", "builder"]
+
+
+def main(prompt: str, config: str = "adws/adw_sssf_config/sssf.config.yaml", adw_id: str | None = None) -> int:
+    cfg = agents.load_config(config)
+    agents.validate(cfg, REQUIRED_AGENTS)
+    run = session.ensure(cfg, adw_id)
+
+    with run.phase(PhaseParams(name="request", kind="engineer", owner=run.engineer,
+                               description="Capture the incoming ask")) as ph:
+        ph.log(input=prompt)
+
+    with run.phase(PhaseParams(name="plan", kind="agent", owner="planner",
+                               description="Turn the request into an implementable plan")) as ph:
+        plan = ph.call(AgentCall(output_type=PlanOutput, prompt=prompt,
+                                 gates=[gates.artifacts_exist, gates.files_non_empty]))
+
+    with run.phase(PhaseParams(name="build", kind="agent", owner="builder",
+                               description="Implement the plan exactly")) as ph:
+        build = ph.call(AgentCall(output_type=BuildOutput, prompt=prompt, previous=plan,
+                                  gates=[gates.diff_matches_claims]))
+
+    with run.phase(PhaseParams(name="commit", kind="code", owner="git",
+                               description="Land the builder's changes, using the message it wrote")) as ph:
+        message = build.commit_message or f"sssf({run.adw_id}): {build.summary}"
+        ph.log(sha=git_helper.commit_all(message), message=message)
+
+    return run.finish()
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("prompt", help="inline text or a path to a prompt file")
+    parser.add_argument("--config", default="adws/adw_sssf_config/sssf.config.yaml")
+    parser.add_argument("--adw-id", default=None, help="join or pin an existing session")
+    args = parser.parse_args()
+    sys.exit(main(utils.resolve_prompt(args.prompt), args.config, args.adw_id))