fix: session not found when selecting sessions from TUI picker

[Limme-swe]

Fixes#12345

Two bugs causing "session not found" when picking sessions in the TUI:

1. The session array gets sorted with localeCompare but Binary.search uses <. These give different orderings for mixed-case strings — and session IDs have base62 random suffixes with mixed case. So binary search just misses sessions that are right there in the array. The app/ package already does this correctly, the TUI sync store and permission sort were the odd ones out.

2. If any message or part file has corrupted JSON, the messages endpoint blows up with a 500 and the catch handler shows "session not found" even though the session is fine. Now stream() and parts() skip unreadable files instead of crashing.

[github-actions]

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[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Based on the search results, I found one potentially related PR:

PR #8825: fix: skip corrupted session files when listing sessions

• fix: skip corrupted session files when listing sessions #8825
• This PR appears to address part of the same issue (corrupted message/part files), which is one of the two root causes in PR fix: session not found when selecting sessions from TUI picker #12343.

The other search results (#6138, #5020, #5518) are related to TUI session handling but address different features/issues (session picker limits, layout system, linear search fallback) rather than the specific bugs in PR #12343.

Recommendation: Check PR #8825 to see if it's already been merged or if it duplicates the corrupted file handling fix in PR #12343.