feat(phase-14/35): add mission.md briefing

phases/14-agent-engineering/35-initialization-scripts/mission.md

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+# Mission - Initialization Scripts for Agents
+
+## Goal
+Build `init_agent.py` that probes runtime, dependencies, test command, env vars, and state freshness, then writes `init_report.json` and halts the session loud when a block-severity probe fails.
+
+## Inputs
+- A repo with a `requirements.txt` (or equivalent), a test command, and the workbench state file from lesson 34
+- The probe table from the lesson (runtime, deps, paths, env, state freshness, last-known-good commit)
+
+## Deliverables
+- `init_agent.py` with one function per probe returning `(name, status, detail)`
+- `init_report.json` carrying the full probe set and a timestamp
+- Non-zero exit on any block-severity probe failure
+
+## Acceptance
+- `python3 code/main.py` exits zero on the happy path
+- Running it twice in a row is a no-op except for the timestamp
+- A simulated missing env var probe surfaces in the report and flips the exit code
+
+## Out of scope
+- Auto-installing missing dependencies. The script halts and surfaces; the human fixes.
+- Calling an LLM from a probe. Probes stay deterministic plumbing.
+
+## References
+- `docs/en.md` - full lesson
+- `code/main.py` - reference implementation
+- `outputs/skill-init-script.md` - extracted skill