Run CI on claude/spec-driven-engine and raise Python floor to 3.12

[MaxGhenis]

What

1. Run CI on claude/spec-driven-engine. The Tests workflow only triggered on main, but the last ~30 PRs (Add provider-backed source registry #44–Resolve observation frames for entity bundles #74) merge into claude/spec-driven-engine — so the entire spec engine has landed with zero CI runs since May 31. This adds the integration branch to the push/pull_request triggers so every PR into it (including this one) runs the suite.

2. Align the Python floor with reality. requires-python claimed >=3.11, but microimpute — the canonical donor-imputation backend the spec engine depends on — only installs on 3.12 <= python < 3.15 via its environment marker, so a 3.11 install silently lacks the imputation engine. This bumps requires-python to >=3.12, drops 3.11 from the CI matrix and classifiers, bumps the docs workflow Python (3.11 can no longer pip install -e .), and aligns the mypy target.

Why now

Flagged in an architecture review (2026-06-09): CI-on-trunk is the highest-leverage safety fix available — it removes the silent-breakage class entirely (the same class that produced the stale packs/us ↔ microplex-us spec divergence).

Notes

• The first run of this workflow on the branch is also the first signal on whether the suite is green after the Emit live calibration telemetry for dataset development dashboard #16–Resolve observation frames for entity bundles #74 merge train; if it is red, that is information this PR exists to surface.
• microcalibrate (the [calibrate] extra) still needs 3.13+; its marker is unchanged.

🤖 Generated with Claude Code

[MaxGhenis]

First full-suite CI run on this branch: 41 failed / 1,029 passed / 123 skipped (after the __init__.py fix made the suite collectable at all — it previously died at collection on the tests/{spec,targets}/test_spec.py basename collision).

All 41 failures are one root cause, not 41 problems:

src/microplex/imputation.py:443: in _make_imputer
    return Imputer(seed=self.seed, log_level="WARNING")
E   TypeError: Can't instantiate abstract class Imputer without an implementation for abstract method '_fit'

The engine instantiates microimpute.Imputer directly as the canonical regime-gated imputer — but on PyPI's microimpute==3.1.1 (what pip install -e ".[dev]" resolves), Imputer is still an abstract base class. The concrete canonical Imputer lives on the unreleased claude/imputer-canonical branch (PolicyEngine/microimpute#196), which is what local dev runs against via the editable install documented in docs/spec-driven-rebuild-progress.md.

So the failures are the declared dependency surface telling the truth: the spec engine cannot run against any released microimpute. Unblock path:

1. Merge Make microimpute.Imputer the canonical regime-gated sequential imputer microimpute#196 and let it auto-release.
2. Bump this repo's pin from microimpute>=3.1.1 to the released version.
3. Re-run — the 41 spec/imputation failures should clear together.

I deliberately did not skip/xfail these tests — masking them would hide exactly the signal this workflow exists to give.

🤖 Generated with Claude Code