fix(cache): cache keys too long to be a filename; memory hits judged by the record's own age

[ChuckBuilds]

Summary

Two cache bugs, found from hdpi's journal and a code review.

1. A cache key too long to be a filename was never cached

• Seen on hdpi: the calendar plugin's key joins every calendar ID the user picked: calendar_events_<6 calendar ids>, over 300 bytes. ext4 caps a filename at 255 bytes.
• Result: every hourly write failed with [Errno 36] File name too long, at all three write stages (temp file, direct write, home-dir fallback).
• Misleading log: the final warning said (permission denied) whatever the error was, so it looked like a cache-directory ownership problem.
• Fix: DiskCache.get_cache_path keeps any key up to 200 UTF-8 bytes as its filename, exactly as before, so existing files keep their names. A longer key becomes its first 183 bytes, cut on a character boundary, plus a 16-hex hash of the whole key.
• The shortened stem is itself short, so the web UI's cache list (which names keys by filename) still deletes the right file.
• The give-up warning now names the real error.

2. The memory tier served data older than the reader asked for

• Cause: a record loaded from disk was timed in memory from the load, not the write. So get(key, max_age=300) could return data close to 600 s old after a restart, after the hourly memory sweep, or in the other process. A stored ttl was stretched the same way. feat(fetch): one ESPN scoreboard cache key and a max-age response cache (fetch service stage 2) #728's _fresh_cached already worked around this for the scoreboard; every other caller was exposed.
• Fix: get_cached_data / load_cache now also check a memory hit against the record's own timestamp, with DiskCache.get's rule that a stored ttl wins.
• A stale copy falls through to disk, which returns the other process's newer write if there is one.
• Records without a timestamp keep the memory tier's own clock.

Tests

• New: test/test_cache_long_keys.py (7) and test/test_cache_memory_tier_age.py (5).
• Mutation check: reverting either fix makes 5 and 2 of them fail.
• Related suites: 547 cache/fetch/odds/health tests pass.

Validation on hardware

• ledpi (ext4): a script with hdpi's key shape. The old module dropped the key; the new one wrote a 205-byte filename and read it back.
• hdpi: read-only for this session. Its journal is where the bug showed: 15 failed calendar writes in 7 days.

Part of a bug sweep

This is one of 10 independent fix PRs from one sweep, all based on main ef69201.

• Merge order: any. 45 pairwise test merges gave 0 conflicts, and each PR also merges cleanly with fix(ipc): ticks carry the volatile timestamps, so current-status stays known over the socket #737.
• CHANGELOG: each PR adds its bullet at a different place in Unreleased → Fixes, so squash-merging them one after another needs no conflict fixing.
• Full suite (Windows), all 10 merged together vs plain main: the same 62 failures and 6 errors on both. These are the known Windows path and file-locking tests. 191 more tests pass.
  • One extra failure in that run, test_backup_manager.py::test_create_backup_contents (os.replace → WinError 5 on a temp zip), was a Windows file-lock flake. It passes on rerun, and nothing here touches create_backup.
• ledpi: all 10 together ran on ledpi (Pi 4) on top of main, with a clean start and no errors or render stalls in the journal. ledpi is back on plain main.

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📥 Commits

Reviewing files that changed from the base of the PR and between ef69201 and d53a898.

📒 Files selected for processing (5)

• CHANGELOG.md
• src/cache/disk_cache.py
• src/cache_manager.py
• test/test_cache_long_keys.py
• test/test_cache_memory_tier_age.py

• Autopilot · Keep fixing CodeRabbit findings and required CI, and resolving merge conflicts

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Up to standards ✅

🟢 Issues 0 issues

Results:
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🟢 Metrics 11 complexity

Metric	Results
Complexity	11

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