feat: add Kitty Graphics Protocol and Sixel support for diagram rendering

[Copilot]

Diagram rendering (c8ctl get pi --diagram) only implemented iTerm2 Inline Images Protocol (OSC 1337), which Ghostty doesn't support. Ghostty requires Kitty Graphics Protocol. Additionally, added Sixel protocol support for legacy terminals.

Changes

• Added supports-terminal-graphics dependency for automatic protocol detection
• Implemented Kitty Graphics Protocol alongside existing iTerm2 protocol:
  • Chunked transmission (4KB) with proper continuation flags (m=0/m=1)
  • PNG format signaling (f=100)
  • Escape sequence: \x1b_Ga=T,f=100,m=X;<base64>\x1b\\
• Implemented Sixel protocol for legacy terminal support:
  • Uses pngjs for PNG decoding and sixel package for encoding
  • 256 color quantization
  • Supports xterm, mintty, mlterm, and other legacy terminals
• Protocol selection: Detects terminal capabilities and uses:
  • Kitty for Ghostty/Kitty/WezTerm/Konsole
  • iTerm2 for iTerm2/VS Code/mintty
  • Sixel for xterm/mintty/mlterm and legacy terminals
• Regenerated package-lock.json from scratch with Node 22 LTS

Example

// Before: only iTerm2 protocol
process.stdout.write(`\x1b]1337;File=${args}:${base64}\x07\n`);

// After: automatic protocol detection and selection
const support = supportsTerminalGraphics.stdout;
if (support.kitty) {
  printKittyImage(pngBuffer);  // Ghostty, Kitty, etc.
} else if (support.iterm2) {
  printIterm2Image(pngBuffer, filename);  // iTerm2, VS Code, etc.
} else if (support.sixel) {
  await printSixelImage(pngBuffer);  // xterm, legacy terminals
} else {
  printIterm2Image(pngBuffer, filename);  // fallback
}

Diagrams now render correctly in iTerm2, Ghostty, and legacy terminals with Sixel support.

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[vobu]

include an implementation for support.sixel (from supports-terminal-graphics) as well

[Copilot]

Added Sixel graphics protocol support in commit b3bfe40. The diagram rendering now supports three protocols:

• Kitty Graphics Protocol for Ghostty, Kitty, WezTerm, Konsole
• iTerm2 Inline Images Protocol for iTerm2, WezTerm, mintty, VS Code
• Sixel protocol for xterm, mintty, mlterm, and legacy terminals

The implementation uses pngjs to decode PNG data and the sixel package to encode it to Sixel format with 256 colors.

[vobu]

redo an "npm install" for Node 22 LTS and redo package-lock.json from scratch

[Copilot]

Regenerated package-lock.json from scratch with Node 22 LTS in commit b3bfe40. Also fixed a missing comma in package.json dependencies that was causing parse errors.