fix(dev): generate the ATW testing dashboard from the entity registry

[andrew-blake]

Summary

Builds on feat/atw-water-temp-report-unification, whose water-temperature behaviour these cards are there to exercise; that branch has no PR number yet, so expect one to replace the branch name here.

tools/build_dev_dashboard.py generates the dev ATW testing dashboard from the live HA entity and device registries: one view per ATW unit, with zone 2 and the device's display name resolved at run time. Entity IDs carry the building name as a prefix, and for real devices that prefix is personal data, so --mock-only limits the output to the mock server's synthetic buildings and that filtered form is what is committed under dev-config-template/.storage/, where it survives make dev-reset. The water-temperature cards cover every vendor-defined series, including the ones #266's capability gating leaves uncreated. Design rationale lives in the module docstring; last_reading semantics are in ADR-022 (docs/decisions/022-reading-provenance.md) and the report source in ADR-023 (docs/decisions/023-atw-water-temperatures-from-report.md).

Risks accepted

Regenerating the committed template without --mock-only writes real building and device names into the repo. The generator's building allowlist only decides which units that flag keeps, so nothing blocks the unfiltered form, and detection rests on diff review at commit time because these names are not a pattern gitleaks matches. Undo is a regenerate with the flag, plus a history rewrite if the leak has already landed.

AI Disclosure

• No AI/agent tooling was used
• AI/agent tooling assisted; I reviewed and ran the change myself before submitting

Testing

• make pre-commit: all 12 hooks pass, gitleaks included.
• --mock-only output is byte-identical to the committed dev-config-template/.storage/lovelace.melcloudhome_testing, so that file is regenerable and holds only the mock server's two synthetic buildings.
• Full run against the live dev registry emits 4 views for 4 ATW units, 2 mock and 2 real, with zone-2 detection firing on the one dual-zone unit.
• 6 of the 77 entity references in that output are absent from the registry, all zone-2 flow and return water temperatures on single-zone units, which is the generator's intended behaviour.
• The unprefixed entity IDs the committed dashboard carried match none of the 177 melcloudhome entities in the live dev registry, spread across 12 entity-id prefixes.
• The ha-melcloud-dev container serves the generated 4-view dashboard with no lovelace or dashboard errors across its startups; its only melcloudhome warnings come from the mock's randomised telemetry.
• make test-api, make test-integration, make test-e2e: not run here; the diff is one dev-only script and a lovelace JSON, neither on a test path.
• Automated coverage for tools/build_dev_dashboard.py: none exists.
• Dashboard confirmed visually in a browser: not done here.
• Prod deployment and soak: not applicable, tools/ sits outside custom_components/ so nothing in this layer ships to users.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.21%. Comparing base (c1a6b47) to head (f8709fc).

Additional details and impacted files

@@                           Coverage Diff                           @@
##           feat/atw-water-temp-report-unification     #276   +/-   ##
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  Coverage                                   93.21%   93.21%           
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  Files                                          44       44           
  Lines                                        2904     2904           
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  Hits                                         2707     2707           
  Misses                                        197      197           

Flag	Coverage Δ
unittests	93.21% <ø> (ø)

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