fix(session): sort messages by time.created instead of alphabetical order

[jchuder]

What does this PR do?

Fixes Session.messages() to sort messages by time.created timestamp instead of relying on alphabetical message ID order.

Fixes #7426

Problem

opencode export <session_id> outputs messages in wrong order for long sessions. The first part of the conversation appears in the middle or end of the export.

Root cause: Session.messages() used result.reverse() which only reverses the alphabetical order from Storage.list(). Message IDs are random strings (e.g., msg_19b9ed* vs msg_b9946c*), so alphabetical order ≠ chronological order.

Fix

Replace result.reverse() with result.sort((a, b) => a.info.time.created - b.info.time.created) to ensure messages are always sorted by creation timestamp.

How did you verify your code works?

1. Ran lsp_diagnostics on changed file - no errors
2. Tested export on a session with 500+ messages - output now correctly ordered by time
3. Verified first message in export matches the actual first message of the session

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1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

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