docs(testing): record the gauge test-shim trap

[mairas]

The gauge library is aliased to a test shim exposing only options and value — there is no update(). Every imperative update() push in the gauge widgets throws into the surrounding catch, so anything asserted only through those pushes is unobservable: a misspelled option key passes CI. Assert the built options, or the extracted decision, instead.

The second trap from #530 (a linear gauge constructed with barProgress: false throws) is not here. It is already commented at both call sites in widget-gauge-ng-linear.component.ts and guarded by a spec, and it only fires when editing that one file — the file whose comment already says it. CLAUDE.md loads in every session; a fact with a local home does not belong in it.

Docs only; no code change.

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📝 Walkthrough

Walkthrough

CLAUDE.md adds guidance for testing canvas-gauges behavior and avoiding initialization errors caused by disabled progress bars or non-positive dimensions.

Changes

Canvas-gauges guidance

Layer / File(s)	Summary
Gauge testing and runtime constraints CLAUDE.md	Documents that the test shim exposes options and value, while update() calls throw and are swallowed. Documents transparent barProgress configuration and positive dimension requirements.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Mergeability Score: 🔵 Low · up to 2888b

The documentation currently conflates a gauge initialization failure with a separately swallowed update failure, which could mislead future debugging. The change is otherwise localized and mergeable once this wording is corrected or explicitly accepted.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title uses the required Conventional Commit form and accurately describes one documented gauge test-shim issue.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch docs/gauge-library-gotchas

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[mairas]

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Actionable comments posted: 1

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Inline comments:
In `@CLAUDE.md`:
- Line 94: Handle LinearGauge construction or initialization failures separately
from the widget update() catch blocks: ensure exceptions from
LinearGauge.ngOnInit() and its initial draw are caught or prevented before
update() is invoked, while retaining the existing handling for update failures.

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📥 Commits

Reviewing files that changed from the base of the PR and between 1a7992f and 2888b90.

📒 Files selected for processing (1)

• CLAUDE.md