Summary

Adds two tightly-coupled TUI capabilities scoped to local and remote modes.

• Filter DSL (/ key): temp>85, util<5 & host~=dgx,
  user==alice | power>400, and similar. Fields, numeric comparisons,
  string equality, size-bounded regex (~=), &/|, and parentheses.
  Unknown fields are parse errors; fields absent on the row fail closed.
  Non-matching rows are dimmed via DarkGrey (hidable via config).
• Threshold alerts: [alerts] config with defaults
  (temp_warn_c=80, temp_crit_c=90, util_idle_pct=5,
  util_idle_warn_mins=15, power_crit_w=0, hysteresis_c=2). Per-
  device per-rule hysteresis state machines emit
  AlertTransition records, which become toast notifications, a 1 Hz
  border flash on the affected tile, and entries in a 50-slot ring
  buffer. Optional async webhook POST (2 s timeout, bounded mpsc queue,
  non-blocking: new alerts are dropped if the worker queue is saturated).
  A toggles the history panel.

Implementation notes

• New modules: src/ui/filter_dsl/{mod,lexer,parser,eval}.rs,
  src/ui/alerts.rs, src/network/webhook.rs,
  src/ui/renderers/dim.rs.
• AppState gains filter_query, filter_buffer,
  filter_input_mode, filter_recent, alerter, alert_history,
  and alert_panel_open — all cloned into RenderSnapshot so the
  render path stays lock-free.
• event_handler intercepts every key while
  FilterInputMode::Editing so that q, d, u, f etc. become
  literal text until the operator commits (Enter) or aborts (ESC).
• Filter dimming avoided rewriting every print_colored_text call by
  post-processing the rendered bytes: dim_ansi replaces every SGR
  foreground with \x1b[90m (DarkGrey) while preserving
  cursor-movement CSI sequences. This keeps existing renderers
  untouched.
• data_collector runs Alerter::evaluate on the GPU snapshot after
  every successful collection, pushes transitions to the notification
  manager + ring buffer, optionally emits a bell (\x07), and
  fire-and-forget POSTs to the webhook channel.
• CLI: --alert-temp and --alert-util-low-mins on both local and
  view. Compiled defaults apply when no config file is present.
• Regex safety: RegexBuilder::size_limit(128 * 1024); over-sized
  patterns surface as parse error: invalid regex: ....

Testing

• 62 parser tests covering success cases for every field, every
  operator, logical combinations, whitespace tolerance, precedence,
  and failure modes (unknown field, type mismatch, unterminated
  parens, oversized regex, invalid regex, trailing garbage).
• 23 eval tests for numeric / string / regex paths, fail-closed
  semantics, GpuInfo, ProcessInfo, and CpuInfo impls.
• Hysteresis boundary tests: ok->warn, warn->crit, no
  transition inside the hysteresis band, recovery to ok, zero
  thresholds disabling the rule, and crit->ok direct recovery when
  the warn rule is disabled.
• Webhook integration test (tests/alert_webhook_test.rs): minimal
  tokio TCP server captures the body, asserts the serialized JSON
  matches the field shape from the issue.
• Event handler tests: / enters edit mode; characters append;
  Enter commits a valid filter and adds to recent; invalid query
  keeps edit mode and surfaces an error; ESC aborts; q is literal
  text while editing; Ctrl-R recalls the newest entry; A toggles
  the alert panel; ESC closes it.
• cargo build, cargo test --lib (678), cargo test --bin all-smi
  (737), cargo clippy --all-targets -- -D warnings, and
  cargo fmt --all -- --check all pass.

Closes #186