feat(inbox): error tracking source, LLM evaluations, source config improvements

[Twixes]

Problem

Signal source config in Code is missing error tracking (which Cloud has with 3 sub-types), shows a non-functional LLM analytics toggle (backend hardcodes return True), and has re-render issues when toggling sources due to useAuthenticatedMutation state churn.

Changes

• Add error tracking source with issue_created/issue_reopened/issue_spiking toggled together
• Replace LLM analytics toggle with a list of evaluations fetched from the API, each individually toggleable – polls every 5s when visible, links to Cloud for full management
• Drop useAuthenticatedMutation in favor of direct API calls with per-source optimistic state – fixes the frame drop on toggle
• Change SignalSourceToggles from onChange(values) to onToggle(source, enabled) with React.memo cards
• Add GitHub OAuth flow in DataSourceSetup when no integration exists (was a dead-end message)
• Add SuggestedReviewer and SuggestedReviewersArtefact types for use in later PRs

[Twixes]

• feat(inbox): show research task logs inline in report detail pane #1413
• feat(inbox): two-pane layout with empty state overlays #1408
• feat(inbox): priority sorting, status filter, suggested reviewers #1407
• feat(inbox): match Cloud signal card wording and structure #1406
• feat(inbox): error tracking source, LLM evaluations, source config improvements #1405 👈 (View in Graphite)
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