feat(tui,monitor): interactive TUI with normal/inspect modes

Adds a scrolling log-pane widget (tui.h/tui.c) and rebuilds
`ice target monitor` on top of it with two user-visible modes plus
a CI-friendly dumb passthrough.

tui_log widget:
- ring-buffered log with bounded scrollback (default 10k lines)
- per-line decorator hook + per-byte SGR overlays for level / keyword /
  search highlighting, composed via a stack-based renderer that nests
  cleanly across hard wraps
- PCRE2 regex search with match counter, current-match marker, and
  forward / backward navigation that survives ring eviction via global-
  index anchoring
- snapshot ceiling so a frozen view stays stable while the ring keeps
  growing in the background

ice target monitor:
- normal mode: pure passthrough, only Ctrl-T intercepted (prefix for
  x=exit, i=inspect, r=reset, p=bootloader, ?=help, Ctrl-T=literal)
- inspect mode: ceiling-frozen view with a vim-style keymap
  (j/k/Up/Down/PgUp/PgDn/g/G/Home/End scrolling, /, n, N for search,
  Esc/q to exit)
- ESP-IDF E/W/I level lines tinted to match the firmware's own
  colouring; default keyword rules (error: / warning: / FAILED: /
  CMake / undefined reference / etc.) applied to non-IDF lines
- title bar shows mode badge and per-mode key hints; help is per-mode
  via tui_info modal
- automatic dumb passthrough when stdout/stdin isn't a tty (CI, piped
  capture, redirection); --no-tui forces the dumb path
- DTR/RTS reset and bootloader sequences match esf_port.c's
  UnixTightReset path

Signed-off-by: Frantisek Hrbata <frantisek.hrbata@espressif.com>

Author: fhrbata