feat(terminal): prompt and command marks from shell integration (#614)

[kipavy]

Closes #614

Problem

Shell integration reports only the working directory (OSC 7). A terminal knows a prompt was drawn, but not where a command's output starts or how the command exited. Jumping between prompts, copying the last output, exit-status marks and output-only decoration (#317) all need that.

Change

Shell hooks (src-tauri/src/shell_integration.rs)

• bash, zsh and PowerShell now send OSC 133 A (prompt start), C (command start) and D;<exit> (finished), for local shells and for SSH, WSL and container sessions.
• D and A ride on the existing OSC 7 printf, so a prompt is still one write. C comes from PS0 in bash, preexec_functions in zsh, and a wrapper around PSConsoleHostReadLine in PowerShell.
• The hook text lived in five copies. It is now built from shared macro_rules! fragments (pwd_fn!, bash_hooks!, zsh_hooks!, zsh_env!, bash_login_chain!, sh_hooks!).
• Comments that were being sent inside the SSH bootstrap moved to Rust doc comments. The persistent payload is under the 8192-byte cap with the new hooks; it measured 7408 bytes before the comments came out.

Frontend

• src/components/terminal/commandMarks.ts: a tracker that turns the marks into command regions (prompt line, output start, end line, exit code, start and end time). Positions are xterm markers, so they follow scrollback trimming.
• useTerminal.ts registers the OSC 133 handler next to the OSC 7 one and exposes getCommandRegions(sessionId).
• Nothing consumes the regions yet. Sessions that send no marks behave as before.

Deviations from the issue

• No B (input start). It is the only mark that needs the user's prompt edited, and no planned feature needs it. The tracker records B when the user's own prompt sends it.
• bash below 4.4 has no PS0, so it sends no C: prompts are tracked, output regions are not.
• POSIX sh fallback and cmd send no marks.
• fish gets no hook and relies on its own marks. Not tested.

Open questions from the issue

• tmux control mode: passes the marks. Checked live on tmux 3.7c with bash and zsh.
• Reattach: the terminal is reset, so the region list restarts empty. The first command typed at the restored prompt is not tracked, because that prompt's A was never replayed.
• Duplicate marks: a prompt marked twice on one line counts once; a second C or D for the same command is ignored.
• Nested shells (ssh, sudo su): the outer command stays open until the outer shell reports again, which is what is happening.

Testing

• cargo fmt --check and cargo clippy --workspace --all-targets -- -D warnings clean.
• cargo test --lib shell_integration: 33 pass. New tests run real bash and zsh (zsh is skipped when not installed) and compare the mark sequence.
• tsc --noEmit clean. 9 new tracker tests; src/hooks suites pass (284 tests).
• Live debug build in a private headless container: local bash, SSH bash without a multiplexer, SSH bash and zsh through tmux control mode. Regions, exit codes and timings matched the commands run.
• PowerShell 7.4.6 on Linux, script run standalone, also under Set-StrictMode -Version Latest.

Not covered

• Windows PowerShell 5.1, WSL and container sessions were not run.
• bash 3.2 (macOS) takes the no-C path; not run.