feature/add: racing against past versions of yourself

[aaravmaloo]

Race Against Yourself

This PR implements local Race Against Yourself mode with saved run history and replay selection, while keeping the TUI minimal.

Summary of the feature

• Persistent local race storage in races.txt (JSON lines).
• Every finished test now saves:
  • typed text/snippet
  • mode/lang/difficulty/duration
  • result stats (wpm, raw, accuracy, mistakes)
  • typing timeline points for replay
• Race history picker: press ctrl+g before test start.
• Selecting a race restores the exact saved context and text, so you race the same content.
• Ghost cursor support in typing view (ghost position rendered in text).
• Race UI simplified:
  • removed verbose bottom race HUD
  • live screen shows only old <wpm> wpm in the top line when race mode is active
  • results screen shows only old race wpm <value>

UX / Behavior Notes

• Race mode stays active across restarts until test config changes (duration / mode / lang / lesson / difficulty), then it resets.
• All race data is fully offline/local and follows existing storage architecture conventions.

Validation

• gofmt run on modified files
• go vet ./... passes
• go build -o toofan . passes
• the feature was tested thoroughly and works as expected

Notes for Reviewers

• Test flow: start app → ctrl+g → pick saved race → type test → verify same text and old WPM display in live/results screens.
• No network calls or new external dependencies added.
• README.md yet to be updated

[vyrx-dev]

raceDelta is never used anywhere

[vyrx-dev]

make sure this follows the newr tab / escape key-binds

[vyrx-dev]

@aaravmaloo can you please look into it 👆

[vyrx-dev]

pushed fixes to the branch:

• removed dead code (raceDelta, normalizeRaceRecord, elapsedAt) — computed but never used
• restored tab/esc keybinds to match master (tab = restart, esc = duration picker)
• old wpm now shows next to wpm on results page, same color as other stats
• removed old wpm from typing screen top line, moved to info line as old 79
• ghost cursor stays visible even when you're ahead (so you can see it closing in)
• ctrl+t opens theme picker without resetting mid-test
• race history capped at 10 entries, newest first
• races.txt included in backup/restore
• esc from results now properly creates a fresh game before showing duration picker

[vyrx-dev]

@aaravmaloo cross check everything and test it locally and see if you find any bugs or anything wrong when it's approved from your side then we'll merge it