Replace internal/ansi with charmbracelet/x/vt emulator

[schovi]

Enhancement

The internal/ansi/ package uses hand-rolled regex stripping, a virtual 2D character grid, heuristic-based TUI frame detection, and a manual terminal responder. This works for common cases but breaks on complex TUI apps with cursor-addressed painting, alt screen interactions, and grapheme clusters. The charmbracelet/x/vt library is a proper VT terminal emulator in pure Go that handles all of this correctly.

Solution

TUI sessions use a vterm.Screen wrapper around charmbracelet/x/vt's thread-safe emulator. PTY output feeds the emulator directly (no raw byte storage). Reads return the current screen state via Render() (ANSI-styled) or String() (plain text). An atomic version counter replaces byte-count change detection. Terminal capability queries (DA1, DA2, DSR) are handled natively by the emulator, with a ReadResponses goroutine bridging responses to the PTY master. Non-TUI ANSI stripping uses a two-path approach: fast regex for simple output, temporary VT emulator for cursor-positioned content.

Changes

New package: internal/vterm/

• screen.go: VT emulator wrapper with version counter and terminal query response bridge
• strip.go: ANSI stripping with fast regex path and emulator fallback for cursor sequences
• screen_test.go, strip_test.go: comprehensive test coverage (60+ strip test cases)

TUI session handling (internal/daemon/server.go):

• TUI sessions create vterm.Screen instead of FrameDetector + TerminalResponder
• captureOutput feeds emulator directly for TUI, raw storage for non-TUI
• handleRead, handleSnapshot, handleSearch, handleSize all branch on TUI mode
• Snapshot uses resize cycle + version settle (no storage clearing or frame detection)

Wait/settle adaptation (internal/wait/wait.go):

• FullOutput flag treats output as full screen content rather than growing buffer
• TUI-aware pattern matching runs against complete screen state

Call site updates (cmd/, internal/mcp/):

• All ansi.Strip() calls replaced with vterm.StripDefault()
• InfoResponse includes TUIMode field for client-side TUI detection

Deleted: internal/ansi/ (5 files, ~2900 lines)

• clear.go: Virtual 2D grid renderer
• strip.go: Regex-based ANSI stripping
• responder.go: Manual terminal query responder
• All corresponding test files

Notes

Testing

Validated against 18 TUI apps across 6 categories (170/171 tests passed):

• System monitors: btop, htop, glances
• File managers: ranger, nnn, yazi, vifm
• Git tools: lazygit, tig
• Editors: vim, less, micro
• Network: weechat, irssi
• Misc: ncdu, newsboat, mc, bat

Net code reduction

20 files changed, +729, -3263 (net -2534 lines)