feat(emulator): Implement DECARM - auto-repeat mode

[gdamore]

Summary by CodeRabbit

• New Features

  • Added keyboard key repeat control. Users can now enable or disable key repetition through terminal escape sequences, allowing precise control over keystroke behavior when keys are held down.

• Tests

  • Added test coverage for disabled key repeat functionality.

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[coderabbitai]

📝 Walkthrough

Walkthrough

The pull request adds an AutoRepeat private mode to the terminal emulator that controls key repetition behavior. The emulator now initializes this mode to On, resets it during soft reset, and modifies key repeat logic to conditionally repeat based on this mode state. A test validates disabled key repeat behavior.

Changes

Cohort / File(s)	Summary
AutoRepeat Mode Implementation vt/emulate.go	Added PmAutoRepeat private mode to emulator state, initialized to On in NewEmulator, reset to On during soft reset. Modified repeatRaw to branch: if AutoRepeat is On/OnLocked, repeat key up to 40 times; otherwise, send key once only if repeat count is zero.
Key Repeat Disable Test vt/tests/key_test.go	Added TestKeyRepeatDisabled to verify that sending escape sequence \x1b[?8l disables key repeating, confirming single key press produces single output instead of multiple repeats.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• chore: Add definitions for more private modes, and ANSI modes #977: Main PR implements and uses the PmAutoRepeat private mode—directly depends on the PmAutoRepeat constant and logic added in this PR.
• fix(emulator): Fix for keyboard repeat #1021: Related work on emulator key-repeat logic in vt/emulate.go; this PR modifies repeatRaw to respect the new AutoRepeat mode, complementing the helper function changes.

Poem

🐰 A rabbit presses keys with glee,
But now they know to let them be—
When AutoRepeat's flipped to "No,"
One tap becomes one gentle flow! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: implementing DECARM (auto-repeat mode) in the emulator by adding a private mode that controls key repetition behavior.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing touches

• 📝 Generate docstrings

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.99%. Comparing base (720eeab) to head (194d81e).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1022      +/-   ##
==========================================
+ Coverage   85.95%   85.99%   +0.03%     
==========================================
  Files          46       46              
  Lines        4834     4840       +6     
==========================================
+ Hits         4155     4162       +7     
+ Misses        528      527       -1     
  Partials      151      151              

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