fix(terminal,parser): accept OSC 52 payloads larger than 1 KiB

[roramirez]

Summary

Copying from a program running over SSH silently did nothing when the text was longer than roughly 750 characters. The remote program sends the clipboard through OSC 52;c;<base64> ST, but mmterm dropped the sequence instead of writing to the host clipboard.

The cause is in the vte dependency: its default no_std feature stores the OSC payload in a fixed 1024-byte ArrayVec and stops accumulating once that buffer is full (Action::OscPut returns early when osc_raw.is_full()). A 981-character selection encodes to ~1308 bytes of base64, so the sequence arrived truncated, BASE64.decode failed, and pending_clipboard_write stayed None — no error, no clipboard update.

Turning the feature off swaps the fixed buffer for a growable Vec, which is what other terminals (Alacritty) do for the same reason. OSC 8 hyperlinks and every other OSC handler benefit from the same lift; nothing in mmterm depended on the 1 KiB cap.

Changes

• Cargo.toml — vte = { version = "0.13", default-features = false }, with a comment recording why the default feature is off.
• Cargo.lock — drops the now-unused arrayvec dependency.
• CHANGELOG.md — entry under [Unreleased] → Fixed.
• src/terminal/parser_test.rs — osc52_write_handles_payload_larger_than_1kb, a regression test built from the exact size that failed in practice (981 chars). It fails on main and passes with the fix.

Design notes: the fix is confined to the dependency's buffer strategy — osc_clipboard in src/terminal/parser.rs is unchanged, so the write/read/invalid-base64 behaviour and their existing tests stay as they were. The parser hot path is untouched; Vec growth only occurs while an OSC sequence is being accumulated.

How to test

Automated:

cargo fmt --check
cargo clippy --locked -- -D warnings
cargo test

New test: osc52_write_handles_payload_larger_than_1kb. Full suite: 1245 tests pass.

Manual (end-to-end):

1. cargo run and SSH into another host from inside mmterm.
2. Run a program there that copies via OSC 52 (Claude Code, nvim with an OSC 52 clipboard provider, or by hand: printf '\033]52;c;%s\a' "$(head -c 900 /dev/urandom | base64 -w0)").
3. Paste into any local application — the full text arrives instead of nothing.
4. Repeat with a short selection to confirm the sub-1 KiB path still works.