chore: release v0.6.0

[szjanikowski]

Summary

• Moves [Unreleased] under ## [0.6.0] — 2026-09-11, updates compare links.
• Adds the missing CHANGELOG entry for Calibration round 2: rubric v2, agent-diff judge input, per-task dimensions, judge-matrix run plan #75 (calibration round 2 engine: agent diff as judge input, per-task assessment_dimensions.json, precheck.sh hook + normalized_score_cap, nasde eval --eval-model/--eval-backend, calibrate publish bundling) and the [#76] link-ref on the Harbor 0.19 entry.
• Stacked on deps: raise the typer floor to >=0.26 (fresh installs died on typer._click) #82 (typer floor fix, the reason 0.5.0 on PyPI fails on a fresh install). Merge deps: raise the typer floor to >=0.26 (fresh installs died on typer._click) #82 first; this PR then reduces to the single changelog commit.

Why 0.6.0, not 0.5.1

cost_usd semantics changed (cache-aware, ADR-014), Harbor 0.13 → 0.19, new judge inputs and CLI flags — a 0.x minor.

Test plan

• [#NN] link-refs: every cited PR is defined at the bottom (script-checked, no dangling refs)
• Unit tests also pass against Harbor 0.22 (462 passed in a scratch venv) — a follow-up bump to >=0.22,<0.23 is planned as 0.6.1 after a smoke run, deliberately not coupled with this release
• CI green
• After merge: git tag v0.6.0 && git push origin v0.6.0 (publish.yml handles TestPyPI → smoke → PyPI → GitHub Release, per docs/RELEASING.md)

🤖 Generated with Claude Code

https://claude.ai/code/session_01UwjBNRxR1vkNGBcETRzdf2