perf(tracking): skip schema migration on warm Tracker::new

[iagogfe]

Summary

• When the tracking DB and a versioned schema marker already exist, open SQLite with only busy_timeout instead of re-running CREATE/ALTER/index probes on every CLI call
• Schema bootstrap still runs fully on cold start / marker miss; bump the marker name when migrations change
• Small but real warm-path win on every tracked command (measured as part of rtk git status latency after the git-side fix)

Test plan

• cargo fmt --all --check && cargo clippy --all-targets && cargo test
• Manual testing: first rtk git status creates .tracking_schema_v3 under the RTK data dir; later processes take the warm open path
• Perf (local, Linux x86_64, release, hyperfine --shell=none, after the git single-porcelain change):
  • incremental gain on top of dual-git removal: roughly ~11.3 ms → ~10.9 ms mean for rtk git status in A/B remeasures
  • absolute effect is machine- and I/O-dependent (SQLite open dominates less than process spawn); treat as order-of-magnitude tens of percent of the residual RTK overhead, not a headline % claim

Important: All PRs must target the develop branch (not master).
See CONTRIBUTING.md for details.

[CLAassistant]

All committers have signed the CLA.

[tapheret2]

Review: perf(tracking): skip schema migration on warm Tracker::new

Files: src/core/tracking.rs
Size: +19 / -0

Notes

• Static pass on the patch: no obvious blockers from the diff alone.

Thanks @iagogfe — independent review on the patch.