Lock the bootstrapped Python environment

[fettpl]

Summary

• install the bundled Python kernel from a reviewed universal uv.lock with an exact CPython patch, uv release, and seven-day dependency cutoff
• include the kernel project, lock, constraints, toolchain, and Termux vendoring helper in bootstrap freshness checks
• build and validate replacement environments before an atomic swap, with rollback and interrupted-swap recovery
• keep Python skills outside the base lock while constraining their resolution and restoring the exact base after every skill change
• validate macOS, glibc, musl, Windows, and real Termux/Bionic environments in CI

Solution design

The bundled base runtime is a dedicated non-package uv project. toolchain.json pins CPython 3.11.15, uv 0.11.33, the release-age cutoff, and the reviewed Termux toolchain. constraints.txt is generated from uv.lock and is used only as a constraint for separately installed skills.

Bootstrap validates lock consistency before reusing a warm environment. A stale environment is rebuilt in a sibling directory, validated, and then swapped into place. The prior environment is restored if staging, activation, or post-activation validation fails. The bootstrap marker records the complete artifact digest, target platform, interpreter identity, and uv version.

Linux detects glibc versus musl before selecting wheel tags. Windows receives a native install lane. Termux uses its system Python because uv-managed CPython is unavailable for Android/Bionic. The exact uv release is built from a checksum-pinned source archive. Exact official Termux builds of lxml, NumPy, psutil, and SciPy are version-checked and copied into the staged venv with PEP 738 Android wheel tags; the remaining locked dependencies are built or installed by uv. Termux CI performs both an online install and a new cached-offline install.

Verification

• npm run refresh-python-lock
• npm run check:python-lock (macOS ARM64/x64, glibc Linux ARM64/x64, musl Linux ARM64/x64, Windows x64)
• npx tsx ../../node_modules/vitest/dist/cli.js --run test/kernel-bootstrap.test.ts (28 tests)
• npm run check
• clean native macOS ARM64 bootstrap with uv 0.11.33 and Python 3.11.15
• clean cached-offline native macOS ARM64 bootstrap
• real aarch64 Termux/Bionic bootstrap with source-built uv 0.11.33, Python 3.14.6, runtime imports, and uv pip check
• second clean Termux/Bionic bootstrap with UV_OFFLINE=true

Risks and rollout

• Existing managed kernel environments rebuild once because the bootstrap schema and full artifact digest changed.
• Termux uses reviewed revisions from its rolling package repository. Native revisions must remain aligned with the Python lock and observe the same seven-day cooldown; the real CI lane fails on drift.
• Building exact uv on Termux increases the Android CI duration.
• Custom PRIME_AGENT_KERNEL_PYTHON environments remain an explicit, non-mutating override.

Fixes #932