dotbot swarm: add over-the-air LH2 calibration (collect/push)

[geonnave]

Summary

• Add dotbot swarm lh2-calibration collect to calibrate a single DotBot over the air (no serial cable): walks the four arena corners, triggers a raw-count capture per corner via swarmit, solves the homography, and saves the calibration under ~/.dotbot/.
• Add dotbot swarm lh2-calibration push <path> to send a saved calibration to the bot over the air. Thin forward to swarmit's calibrate-lh2, which picks the payload format (legacy .out or calibration-*.toml) by extension.
• collect takes an optional --tag <label> (e.g. office-2x2m): a filename-safe slug of it is added to the saved filename and recorded under [metadata], so calibrations stay self-describing per arena.
• Serial-cable (single DK) calibration and the C-header apply export stay under dotbot run lh2-calibration.

The homography solve lives here (dotbot.calibration); the transport lives in swarmit. So collect runs natively and push reuses swarmit's command. Transport selection (running server vs in-process controller) is swarmit's auto-detection, so there is no flag to choose it.

Dependency

Runtime needs the swarmit ota-lh2-capture branch, which adds request_lh2_capture, the LH2_CALIB_TAG log payload, and the bootloader / net-core capture trigger. Merge swarmit first. The unit tests here drive a fake client, so this PR's CI is green without it.

Docs

Intentionally not in this PR yet. The CLI-reference / guide / README sweep lands after review, before merge.

Test plan

• dotbot swarm lh2-calibration collect --device <addr> -d <mm> against a bot in READY: all four corners capture, a TOML is saved.
• --tag office-2x2m appears in the filename and in [metadata].tag.
• dotbot swarm lh2-calibration push <toml> sends, and the bot reports a position in dotbot swarm status.
• --push one-shot path on collect sends without a separate push.
• dotbot run lh2-calibration still offers serial collect + apply (no collect-ota).

[geonnave]

Tested on hardware - it works!! Merge after #270.

[codecov]

Codecov Report

❌ Patch coverage is 58.23529% with 71 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.35%. Comparing base (09a1c33) to head (6c8db27).
⚠️ Report is 2 commits behind head on develop.

Files with missing lines	Patch %	Lines
dotbot/cli/swarm_lh2.py	24.13%	66 Missing ⚠️
dotbot/cli/swarm.py	0.00%	4 Missing ⚠️
dotbot/tests/test_calibration_ota.py	98.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #271      +/-   ##
===========================================
- Coverage    83.74%   83.35%   -0.40%     
===========================================
  Files          116      118       +2     
  Lines        10793    10963     +170     
  Branches       570      570              
===========================================
+ Hits          9039     9138      +99     
- Misses        1751     1822      +71     
  Partials         3        3              

Files with missing lines	Coverage Δ
dotbot/cli/calibrate.py	87.17% <ø> (ø)
dotbot/tests/test_calibration_lighthouse2.py	100.00% <100.00%> (ø)
dotbot/tests/test_calibration_ota.py	98.00% <98.00%> (ø)
dotbot/cli/swarm.py	66.66% <0.00%> (-15.69%)	⬇️
dotbot/cli/swarm_lh2.py	24.13% <24.13%> (ø)

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[geonnave]

Validated on hardware end to end, all works.
Does not include docs, as we will merge this and then rebase #270 on this, and update docs there.