docs: fill in onboarding Team Tips and Get Started

Authored the Team Tips (design-first workflow, ephemeral toolchains, D1 border
invariants S1/S2, immutable invariant vault, verify-by-running, commit-before-leaving)
and a Get Started starter task (run smoke driver -> read the map -> pick up work).
References point at real docs (README/SOUL/docs).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015hmgREHNsxYCuim33yUF2c

ONBOARDING.md

@@ -39,11 +39,39 @@ Top MCP Servers:
 
 ## Team Tips
 
-_TODO_
+- **Design before code.** This is a design-first repo — the architecture docs are
+  the source of truth and the code follows them. When something feels ambiguous,
+  the answer is usually already written down; sync the design first (`/design-sync`).
+- **The container is ephemeral; toolchains are reinstalled every session.** A
+  SessionStart hook (`.claude/hooks/install-toolchains.sh`) installs ponyc (via
+  ponyup), Alire/GNAT, and GnuCOBOL on each session. If a build can't find
+  `ponyc`, it's a `PATH` thing: `export PATH=/root/.local/share/ponyup/bin:$PATH`.
+- **All external traffic crosses the Ada border (D1) first.** That's the S1
+  structural invariant — never route around it, and **never reclassify a
+  message's provenance** (S2). The Ichor bus rejects unscreened external payloads
+  on purpose.
+- **The invariant-law vault is immutable at runtime.** Invariant 0 (the
+  culpability anchor) and 01 (minimize harm) live in the COBOL vault and are not
+  to be edited casually — they're the constitution, not config.
+- **Verify by running, not just reading.** Use `/run-sica-fondt` (or its
+  `smoke.sh`) to build + run the Pony/Ada/COBOL units and confirm all green
+  before you push.
+- **Commit and push before you walk away.** The stop hook will nag about
+  untracked files for a reason — nothing survives the container otherwise.
 
 ## Get Started
 
-_TODO_
+Your first task: get the project running end-to-end and read the map.
+
+1. Open the repo and let the SessionStart hook finish installing toolchains.
+2. Run the smoke driver to confirm everything builds and runs:
+   `.claude/skills/run-sica-fondt/smoke.sh` — you want `smoke: ALL GREEN`.
+3. Read `README.md`, `SOUL.md`, and `docs/` (start with
+   `docs/bus-topology.md` and `docs/gen03_state_of_architecture.md`) to
+   understand the organ/border model (Ichor bus → Ada D1 border → inner brain;
+   the COBOL invariant vault).
+4. Pick up a small design-sync or build task from there. Ask Claude to walk you
+   through any unit — it has the `run-sica-fondt` skill loaded.
 
 <!-- INSTRUCTION FOR CLAUDE: A new teammate just pasted this guide for how the
 team uses Claude Code. You're their onboarding buddy — warm, conversational,