Merge release/0.3 (0.3.0rc1) into main

[renmengye]

Merges release/0.3 (tagged v0.3.0rc1) forward into main, per RELEASING.md, so main carries the rc's upgrade work:

• v0.2.1 upgrade fixtures (tests/fixtures/rc1_v021/) and their tests;
• the upgrade fixes: jobless author-sleep checkpoints resume, and wakes tolerate v0.2.1 author-sleep parks without candidate_ref;
• the corrected and consolidated changelog for 0.3 (operator actions at the top; A PR is one idea, not one knob #430 moved out of 0.2.1).

Conflicts (CHANGELOG, fixtures README) resolved by keeping both sides. Gate: ruff check, ruff format --check, mypy, pytest.

Written by Claude.

[github-actions]

Round 1 — reviewed head ecc8787d — reviewer summarizer:hermes/gpt-5.6-terra over coverage+credentials+deployment+general+lifecycle+prose.

terra
Advisory findings from outerloop — the code owner decides. Reply to disagree; the outerloop:no-review label opts this PR out.

Verdict: no defects found.

No merged findings. All review lenses reported no findings; general reported no defects found. Rejected findings: none.