Fix compilation with latest ghostty-vt

[JNSFilipe]

Renames 'ghostty_vt.ReadonlyStream' to 'ghostty_vt.TerminalStream' to fix the compilation error in 'src/gterm.zig'. Also updates the documentation in 'CLAUDE.md' to reflect this change.

[Copilot]

Pull request overview

Updates the Emacs libgterm Zig module to compile against the latest ghostty-vt API by adopting the renamed stream type, and aligns project documentation with the new type name.

Changes:

• Replace ghostty_vt.ReadonlyStream with ghostty_vt.TerminalStream in GtermInstance.
• Update CLAUDE.md to reference TerminalStream in the “Persistent VT Stream” section.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/gterm.zig	Switches the stored VT stream type to ghostty_vt.TerminalStream to match the updated dependency API.
CLAUDE.md	Updates documentation to reflect the TerminalStream type name used by the implementation.

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[rwc9u]

Thanks for the PR! There are some nice improvements in here — the dirty tracking, property batching, and timer change all make sense.

That said, this bundles quite a bit under a "fix compilation" title. Would you be open to splitting it up? Something like:

1. Compilation fix — the ReadonlyStream → TerminalStream rename. Could merge this right away.
2. Dirty tracking — isDirty()/clearDirty(), the new exports, and the elisp refresh loop changes.
3. Property batching — the put-text-property → add-text-properties optimization.
4. Cleanups — declare-function additions, variable renames, timer change.

Splitting them out makes each easier to review, test, and bisect if anything regresses.