release: prepare v0.1.0a2

[edkerk]

Summary

Roll-up commit for the second public alpha. Bumps the version, adds the CHANGELOG entry, ships the MIT LICENSE text the pyproject already declared, drops the redundant requirements.txt, and tucks internal planning notes under docs/internal/ so the user-facing docs/ tree only carries reference documentation.

What landed in 0.1.0a2 (covered by this entry's CHANGELOG)

• gecko-light ecModel end-to-end (#20)
• YAML I/O + typed EcData delegated to raven-python; SBML ecModel I/O removed (#19)
• ec_fseof re-aligned with raven_python.analysis.fseof (#21)
• get_conc_control_coeffs solver-state guard fix (bc1a37d)
• raven-python pin moved from @main to @develop

Housekeeping in this PR

Change	Why
LICENSE added	MIT was already declared in pyproject.toml and the classifier, but no LICENSE text file shipped. Blocks GitHub repo metadata and any future PyPI publish.
requirements.txt removed	Was a pip freeze snapshot duplicating pyproject.toml's declared dependencies. pyproject is the source of truth.
docs/internal/ created	brenda_refresh_plan, code_review, openkineticspredictor_plan, porting_plan, raven_inventory moved out of the user-facing docs/ tree. Two source-file docstrings updated to point at the new location.
pyproject.toml version	0.1.0a1 → 0.1.0a2

Release smoke

• Full pytest suite green: 1259 passed, 1 skipped (network), 1 deselected (opt-in smoke), 1 xfailed (documented).
• Light tutorial runs end-to-end against ecTestGEM.
• Both tutorial scripts compile cleanly. The full tutorial's end-to-end run is exercised piecewise by the unit suite; a live BRENDA + DLKcat + sensitivity-tuning replay was skipped for the release smoke (10+ min, no signal beyond the unit tests).

Post-merge release steps

1. Fast-forward main to develop's tip.
2. Tag v0.1.0a2 on main.
3. Push main + tag.
4. Draft GitHub release pointing at v0.1.0a2 — .github/workflows/release.yml builds sdist + wheel and attaches them. PyPI publish stays disabled (geckopy name is taken on PyPI).