[deep-report] Fix day-keyed cache lookups in Copilot Opt and Copilot Agent PR Analysis

[github-actions]

Description

Daily Cache Strategy Analyzer (discussion #53466) found that Copilot Opt and Copilot Agent PR Analysis restore cache-memory correctly (run_id-scoped key + restore-prefix fallback) but then gate reuse on exact-date filenames (copilot-sessions-${TODAY}.json, copilot-prs-${TODAY}.json, session-logs-${TODAY}/). Since Copilot Opt runs weekly and Copilot Agent PR Analysis runs daily, restored prior-run content almost never matches today's exact date, so both workflows behave like same-day rerun caches instead of real cross-run caches — re-fetching data every scheduled run. This is the identical root-cause pattern (day-keyed cache lookup vs. multi-day run cadence) just fixed for deep-report's own data fetch in PR #53486/#53460.

Expected Impact

Cuts redundant re-fetching of Copilot session/PR data on every scheduled run, reducing token usage and step time, and fixes Copilot Agent PR Analysis's Fetch Copilot PR data step which failed in run 32054193614 (partial/inconsistent cache refresh on a miss day).

Suggested Fix

Replace exact-date cache lookups with a stable "latest" filename or a newest-file-after-restore selection, decoupling cache filenames from the current date (mirrors the fix pattern already applied in #53460/PR #53486).

Suggested Agent

General-purpose / whoever owns .github/workflows/copilot-opt.md and .github/workflows/copilot-agent-pr-analysis.md (or equivalent shared cache-memory helper).

Estimated Effort

Quick (< 1 hour) — same fix pattern as the just-merged PR #53486.

Data Source

DeepReport analysis, 2026-08-18 cycle, discussion #53466 (Daily Cache Strategy Analyzer).

Generated by 🔬 Deep Report · agent · 184.1 AIC · ⌖ 10.5 AIC · ⊞ 11.9K · ◷

• expires on Aug 19, 2026, 4:37 PM UTC-08:00

[github-actions]

🍪 Issue Monster selected this for Copilot

I've identified this issue as a good candidate for automated resolution and requested assignment to the Copilot coding agent.

If assignment succeeds, the Copilot coding agent will analyze the issue and create a pull request with the fix.

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🍪 Om nom nom by Issue Monster · gpt54 · 3.05 AIC · ⌖ 9.25 AIC · ⊞ 10.3K · ◷