fix(tui): termux-gate scrollback preservation, touch-friendly defaults

Adds a Termux runtime detection helper and gates three TUI defaults on it:

- Skip the startup scrollback clear on Termux so users can review/copy
  earlier output after reopening the app. Desktop keeps the existing
  \x1b[2J\x1b[H\x1b[3J slate (AlternateScreen takes over there anyway).
- Default INLINE_MODE on under Termux: primary-buffer rendering makes
  long-thread review and copy/paste much less fragile when users
  background/foreground the app. Override with HERMES_TUI_INLINE=0/1.
- Default mouse tracking off under Termux so touch selection isn't
  intercepted by terminal mouse protocols. Explicit override via
  HERMES_TUI_MOUSE_TRACKING=0/1; legacy HERMES_TUI_DISABLE_MOUSE still
  works on desktop.

Detection is purely env-based (TERMUX_VERSION or PREFIX path) with an
explicit opt-out HERMES_TUI_TERMUX_MODE=0 for debugging. Non-Termux
platforms keep every existing default.

Co-authored-by: adybag14-cyber <252811164+adybag14-cyber@users.noreply.github.com>

ui-tui/src/config/env.ts

@@ -1,16 +1,51 @@
+import { isTermuxTuiMode } from '../lib/termux.js'
+
 const truthy = (v?: string) => /^(?:1|true|yes|on)$/i.test((v ?? '').trim())
+const falsy = (v?: string) => /^(?:0|false|no|off)$/i.test((v ?? '').trim())
+
+const parseToggle = (v?: string): boolean | null => {
+  const raw = (v ?? '').trim()
+
+  if (!raw) {
+    return null
+  }
+
+  if (truthy(raw)) {
+    return true
+  }
+
+  if (falsy(raw)) {
+    return false
+  }
+
+  return null
+}
+
+export const TERMUX_TUI_MODE = isTermuxTuiMode()
 
 export const STARTUP_RESUME_ID = (process.env.HERMES_TUI_RESUME ?? '').trim()
 export const STARTUP_QUERY = (process.env.HERMES_TUI_QUERY ?? '').trim()
 export const STARTUP_IMAGE = (process.env.HERMES_TUI_IMAGE ?? '').trim()
-export const MOUSE_TRACKING = !truthy(process.env.HERMES_TUI_DISABLE_MOUSE)
+
+const mouseTrackingOverride = parseToggle(process.env.HERMES_TUI_MOUSE_TRACKING)
+const mouseTrackingDisabledLegacy = truthy(process.env.HERMES_TUI_DISABLE_MOUSE)
+// Mobile selection UX: on Termux default mouse tracking OFF so touch selection
+// is less likely to be intercepted by terminal mouse protocols. Desktop keeps
+// prior behavior unless explicitly overridden.
+export const MOUSE_TRACKING =
+  mouseTrackingOverride ?? (TERMUX_TUI_MODE ? false : !mouseTrackingDisabledLegacy)
+
 export const NO_CONFIRM_DESTRUCTIVE = truthy(process.env.HERMES_TUI_NO_CONFIRM)
 
+const inlineOverride = parseToggle(process.env.HERMES_TUI_INLINE)
+
 // Skip AlternateScreen — TUI renders into the primary buffer so the host
 // terminal's native scrollback captures whatever scrolls off the top.
-// Experiment gate: lets us measure native scroll vs our virtualization on
-// the same pipeline.
-export const INLINE_MODE = truthy(process.env.HERMES_TUI_INLINE)
+//
+// On Termux we default this on: users often background/foreground the app,
+// and primary-buffer rendering makes long-thread review and copy/paste much
+// less fragile. Override explicitly with HERMES_TUI_INLINE=0/1.
+export const INLINE_MODE = inlineOverride ?? TERMUX_TUI_MODE
 
 // Live FPS counter overlay, fed by ink's onFrame (real render rate, not a
 // synthetic timer).