fix(opencode): scan sqlite database without legacy session dir

[mirsella]

Summary

• keep scanning configured extra session files when a provider session directory is missing
• restore Opencode collection from ~/.local/share/opencode/opencode.db for installs without storage/session
• add regression coverage for extra-file-only providers

Tests

• zig build
• zig build test
• zig build -Doptimize=ReleaseFast
• zig-out/bin/tokenuze --agent opencode --sessions --log-level debug

[gemini-code-assist]

Code Review

This pull request modifies the session event collection in src/providers/provider.zig to ensure that extra session files are still scanned even if the main sessions directory is missing or cannot be opened. It also improves error logging when session IDs fail to build or are empty, and adds a unit test to verify this behavior. Feedback on the changes highlights a potential memory leak where a duplicated path string is not freed if appending to relative_paths fails with an out-of-memory error.

[gemini-code-assist]

If relative_paths.append fails with error.OutOfMemory, the newly allocated copy will be leaked. Adding an errdefer right after the allocation ensures that copy is freed if the append operation fails.

                    const copy = try shared_allocator.dupe(u8, relative_path);
                    errdefer shared_allocator.free(copy);
                    try relative_paths.append(shared_allocator, copy);

[mirsella]

Fixed in 7143445 by freeing duplicated relative paths if append fails, and applying the same guard to configured extra session file paths.