chore: add 'no symptom patching' rule + fix timezone-fragile test#471
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Two unrelated cleanups bundled because they're both tiny. CLAUDE.md — new "Debugging & root cause" section codifying a recurring anti-pattern we saw in PR #460 ("fix forward sheet freeze") and PR #455 ("wrap reads in remember to prevent layout crash"): observe a freeze / ANR / unexplained behaviour, ship a workaround that hides the symptom, move on. The rule: capture concrete evidence (stack trace, ANR dump, profiler sample, repro test) before fixing, and if you can't capture evidence, install the instrumentation that will. Lists four named anti-patterns drawn from real cases so it's clear what's prohibited. MessageProcessingPipelineTest.kt — fix `messagesOnSameDay_shareOneSection` which fails locally in CPH and any TZ east of UTC+0:47. Root cause: `baseTime = 1_700_000_000_000L` decodes to `2023-11-14T22:13:20Z`. The test creates messages at offsets 0/30/60 minutes; in UTC+1 the +60min message lands at 00:13 the next day, producing 2 sections instead of 1. Pinned baseTime to noon UTC (1_699_963_200_000L) so offsets up to ±12h stay on the same calendar date. Other tests in the file deliberately cross day boundaries (24h, 25h offsets) and still do. CI runners default to UTC so this never surfaced there. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Two unrelated cleanups bundled because they're both tiny.
CLAUDE.md — new "Debugging & root cause" section codifying a recurring anti-pattern we saw in PR #460 ("fix forward sheet freeze") and PR #455 ("wrap reads in remember to prevent layout crash"): observe a freeze / ANR / unexplained behaviour, ship a workaround that hides the symptom, move on. The rule: capture concrete evidence (stack trace, ANR dump, profiler sample, repro test) before fixing, and if you can't capture evidence, install the instrumentation that will. Lists four named anti-patterns drawn from real cases so it's clear what's prohibited.
MessageProcessingPipelineTest.kt — fix
messagesOnSameDay_shareOneSectionwhich fails locally in CPH and any TZ east of UTC+0:47. Root cause:baseTime = 1_700_000_000_000Ldecodes to2023-11-14T22:13:20Z. The test creates messages at offsets 0/30/60 minutes; in UTC+1 the +60min message lands at 00:13 the next day, producing 2 sections instead of 1. Pinned baseTime to noon UTC (1_699_963_200_000L) so offsets up to ±12h stay on the same calendar date. Other tests in the file deliberately cross day boundaries (24h, 25h offsets) and still do. CI runners default to UTC so this never surfaced there.