Key bad-credentials notice cooldowns by error code

[Just-Insane]

Summary

Follow-up to #32, which merged before this was caught by a delayed Codex review pass on that PR (linking here since #32's own thread is now closed): comment.

That PR's resend-cooldown fix (itself a fix for a different bug: sentBadCredentialsNotice never resetting since handlePossible40002 doesn't log the user out) didn't distinguish which error code was last notified. Concretely: if a 40002 notice sends successfully, a real 4004 full logout arriving within the following hour would get suppressed by the 40002's resend cooldown — leaving the user staring at "you do not need to log in" advice even though their token was actually just cleared and they do need to log in now.

badCredentialsNoticeAttemptDecision now takes both the incoming and last-notified error codes; the cooldowns only apply when they match. A different code always gets through immediately, since it may carry materially different (even opposite) recovery instructions.

Test plan

• go build ./... / go vet ./... / gofmt — clean
• go test ./... -race — clean
• New test cases covering both cooldowns bypassed when the error code differs from the last notified one.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR refines the bad-credentials notice cooldown logic so the cooldown only suppresses repeat notices for the same underlying Discord error code, preventing stale/incorrect recovery instructions from being shown when a different invalidation scenario occurs shortly after.

Changes:

• Track lastBadCredentialsErrorCode on User and reset it on successful Login.
• Update badCredentialsNoticeAttemptDecision to bypass cooldowns when the incoming error code differs from the last-notified code.
• Extend unit tests to cover cooldown bypass when error codes differ.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
user.go	Adds per-last-error-code tracking and updates cooldown gating to only apply when error codes match.
user_notice_test.go	Adds test cases validating that differing error codes bypass active cooldowns.

Comments suppressed due to low confidence (1)

user.go:2378

• time.Now() is called twice while holding bridgeStateLock (once for the cooldown decision and again when recording lastBadCredentialsNoticeAttempt). Using a single timestamp avoids minor inconsistencies and makes the state update easier to reason about (especially around cooldown boundaries).

	attempt, skipReason := badCredentialsNoticeAttemptDecision(user.sentBadCredentialsNotice, errorCode, user.lastBadCredentialsErrorCode, user.lastBadCredentialsNoticeAttempt, time.Now())
	if !attempt {
		user.bridgeStateLock.Unlock()
		log.Debug().Bool("notice_sent", false).Msg("Bad credentials event (" + skipReason + ")")
		return

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