docs: update CHANGELOG -- 2.0.0 hasn't shipped yet, add everything since

[petercorke]

Summary

• The ## [2.0.0] - 2026-08-17 entry read as if 2.0.0 had already shipped -- it hasn't (PyPI's latest published release is still v1.1.0; pyproject.toml is already at 2.0.0 locally, and the earlier release/v2.0.0rc1 rehearsal branch never went further than a rehearsal).
• 12 more PRs merged since that entry was written weren't reflected at all: the desc= -> label= rename (deprecated, not removed), the s screenshot hotkey, Slider's cb becoming optional, Label(compact=), full Python 3.10+ type hints across the public API, docs now actually built and published via GitHub Pages (the workflow existed only in name before -- the site had never had a successful build), three real bug fixes (legacy robot.q/robot.qd integration not writing back, a disconnect-timeout fallthrough in _send_socket(), run()'s crash-out behavior on a mid-step() disconnect), and the manylinux_2_28 wheel fix.
• Renamed the section to ## [Unreleased] — targeting 2.0.0 (dropping the specific date, which was when the rewrite merged to main, not an actual release date) -- this becomes the real ## [2.0.0] - YYYY-MM-DD entry once that release actually ships.
• Left out CI/internal-only churn with no net user-facing effect: the ccapture.js 2.0.0 dependabot bump and its own revert (net zero), the examples smoke test, and the dependabot npm-path config fix.

Test plan

• Reviewed the full file for accuracy against gh pr list --state merged --search "merged:>=2026-08-18"
• Confirmed pyproject.toml's version (2.0.0) and PyPI's actual latest release (v1.1.0, via pip index versions swift-sim) to get the "not yet shipped" framing right