feat(pasqal): python provisioning — activation venv + AMICO_PYTHON injection

[kateebonner]

Implements the Slack-thread decision (option 1: extension-provisioned venv; Aaron + Kate aligned). Issue to be filed from the thread — will re-title fix(#NN) when it exists.

Summary

Fresh installs cannot connect to Pasqal: the fork's validator spawn resolves $AMICO_PYTHON → bare python3, no ambient interpreter has pasqal-cloud, the validator exits 1 ("SDK not installed"), and the panel misrenders the config lane as "Service unreachable" (found live-testing v0.0.3-alpha; root-caused against the shipped amicode.8 binary, whose AMICO_PYTHON support was verified live before this was written).

• Provisioning owner: the extension. pasqal_python.ts (mirrors pasqal_assets.ts): probe host python3 ≥ 3.10 (PATH + well-known absolute candidates — Dock-launched VS Code inherits the launchd-minimal PATH), -m venv under <opsDir>/venvs/pasqal-connector, pip install -r the staged requirements.txt. Hash-gated: stamp written only after pip exit 0, so failed provisions retry free next activation; fast path is stat+hash, zero subprocesses.
• Env seam / S37 exception: injected via the single buildServerSpawnEnv builder used by all three spawn sites (boot, solver-mode respawn, vault respawn) — no respawn path can drop it. S37 ("no AMICO_* env propagation") note amended in place: this is server-child plumbing for the fork's validator spawn, NOT amico-run contract; amico-run still receives nothing via env.
• Fail-closed AMICO_PYTHON: provisioning failure never sets the var (absent, not empty — the fork's fallback is byte-identical to today), logs ONE actionable line per lane (no python / venv failed / pip failed-offline). Slow path runs in the background, never blocks activation; on success it mutates the live spawn env (ServerManager re-reads at start()) and bounces via the existing amicode.restartServer, so a fresh install self-heals without a reload.
• Override precedence: host $AMICO_PYTHON wins outright and skips provisioning (the $AMICO_PASQAL_VALIDATOR convention; absent-not-empty semantics match the fork's resolver).
• Token safety: provisioner child env is built from scratch as { PATH, HOME } — poison-token test proves no secret rides argv, env, or failure copy.

Freeze respected

release.yml untouched, no tag cut. amico-run argv contract untouched. launch.ts zero-line diff. Unprovisioned sessions: buildServerSpawnEnv output byte-identical.

Deferred (out of scope)

Fork-side rendering of the config-lane error text (panel currently shows state-generic "Service unreachable" copy; the route already returns the precise message). amico-pasqal launcher interpreter unification (submit path). Windows venv layout (lock targets darwin-arm64/linux-x64 only). Staging of the 3 submit-path connector scripts.

Gate results

• extension vitest: 713 pass / 15 skip (+13: 10 pasqal_python incl. real-interpreter venv lane, +1 server_auth, +3 gate mutation) · tsc --noEmit clean · prettier clean
• boot smoke: [smoke] PASS (vendored v1.17.3-amicode.8)
• new behavioral gate assert_provisioned_python.mjs (mirrors assert_packaged_cli.mjs): local run 4/4 PASS — pin parse, real venv+pip from shipped assets, SDK import at ==0.23.0, validator env-guard smoke. Wired in ci.yml only: fast job (source lane) + vsix-gate job (assets unzipped from the real artifact).
• Julia solve E2E: n/a (no template/Julia changes)

🤖 Generated with Claude Code

[kateebonner]

Verification record (merging on this evidence):

• CI: green — including both new provisioning-gate lanes (source-staged in fast, artifact lane in vsix-gate against the unzipped .vsix), each doing a real venv + PyPI install + SDK import at the pin on clean ubuntu runners.
• Unit: extension vitest 713 pass / 15 skip (+13 this PR: provisioning module incl. real-interpreter lane + poison-token/env-allowlist adversarial lanes, seam test, gate mutation tests) · tsc clean · prettier clean · boot smoke PASS on vendored amicode.8.
• Sandbox E2E on the CI artifact (isolated $HOME, no AMICO_PYTHON anywhere): staged → background-provisioned in ~145s cold → venv imports pasqal-cloud 0.23.0 → self-heal restart delivered AMICO_PYTHON=<venv python> into the live server env → real-credential Pasqal connect succeeded (state connected, FRESNEL devices enumerated, token-only pasqal.json at 0600). Second boot takes the stat+hash fast path (zero subprocess); a requirements change re-provisions (stamp rotates); a genuine disk-full pip failure exercised the no-stamp retry lane and recovered on the next activation.
• Known transient (deferred, fork-side): on a truly fresh machine the first ~2.5 min before self-heal completes can still fail a very eager first connect with the generic "unreachable" copy — the fork-side error-rendering fix covers this window.

🤖 Generated with Claude Code