fix: deep-link PR attention actions

[whoisasx]

Summary

• normalize GitHub issue-shaped PR URLs to /pull/{number} before rendering PR links
• deep-link requested-change attention to review comments/files when no direct discussion URL is available
• deep-link merge-conflict attention to GitHub's /conflicts page
• make dashboard session cards allow nested attention links to be clicked directly

Fixes #2198

Tests

• npm run test -- pr-display.test.ts pr-hydration.test.tsx
• npm run typecheck

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[whoisasx]

[harshitsinghbhandari]

LGTM. Clean vertical slice: fetch submitted reviews from GitHub, persist them in the new pr_reviews table, thread them through to the dashboard so attention chips deep-link to the right place (the review, /conflicts, or the failing check). The issue-shaped-URL normalization (/issues/N -> /pull/N) is a nice root-cause fix, and switching the board card to role=button so nested links are clickable is the correct call.

The large diff is mostly the unavoidable cost of plumbing a new persisted entity through the signatures, not gold-plating. Verified the edge cases hold up: an APPROVED review correctly supersedes an earlier changes_requested, and bot-only attention no longer trips HasUnresolvedHumanComments.

Nit (non-blocking): prBaseUrl is a pure alias for prURL and prSubpageUrl is a single-value helper with one caller; both could inline. Not worth holding the PR.

[neversettle17-101]

Code LGTM - let us discuss on the UI part offline