fix(mobile): give a sideways drag on the terminal to the session swipe alone

The terminal's touch handler and the session swipe judged every gesture separately, so a sideways flick also ended as a tap on the session being left (a link, a CLI click, a keyboard toggle) or as a vertical scroll. The terminal now locks the dominant axis past the tap slop, hands a sideways drag it cannot pan to the swipe and publishes the axis, and the swipe stands aside for scrolls, pans, a lift the terminal consumed (its selection gesture), touch selections, a second finger and surfaces with controls of their own. A touch that starts outside the terminal resets the published axis, so swiping from the phone home screen into a session keeps working after a terminal scroll. A deliberate swipe gets 500ms instead of 300ms, and vertical drift cancels it mid-gesture instead of only at the lift.

docs/architecture-invariants.md

@@ -928,7 +928,9 @@ Further detail: the design follows Apple's [Designing for iPhone Duo](https://de
 
 ⚠️ **Long-press selects** by driving xterm's public `select()` (renderer-independent — under WebGL the glyphs are pixels and native selection cannot exist), drag or a further tap extends, and Copy goes through `copyTerminalSelection()` for its execCommand fallback on plain-HTTP installs. Three guards are load-bearing and each came from a real phone: the compat mouse pair after `touchend` (xterm focuses on mousedown and SelectionService resets the model there, so the keyboard sprang up and the selection vanished on lift), the platform's own ~500ms long-press (Android Chrome focuses the nearest editable element — the helper textarea — through no event a handler can preventDefault, so a bounded focus guard blurs it and `contextmenu` is suppressed for the gesture window), and `copyTerminalSelection()`'s closing `terminal.focus()` (right on desktop, wrong on a phone).
 
-Tests: `test/terminal-touch-tap.test.ts`.
+⚠️ **A sideways drag belongs to the session swipe**, never to a tap or a scroll. The touch handler locks the dominant axis on the first travel past the tap slop (`panAxis`: `y` scrolls the buffer, `x` pans a terminal wider than its box, `swipe` when it cannot pan) and publishes it per gesture as `app._terminalGestureAxis`; a `swipe` drag is consumed without scrolling and never ends as a tap, which used to activate a link, a CLI click or a keyboard toggle on the session being left. `SwipeHandler` (mobile-handlers.js) reads that axis and stands aside for `x` and `y`, for a touch selection, after a second finger, and on surfaces with controls of their own (`IGNORE_SELECTOR`: the tile grid, the selection bar, the CJK input, the history banner); the phone overview and the welcome screen are deliberately not listed, since swiping from home into a session is a feature. A swipe is 80 px of travel within 500 ms (300 ms rejected an unhurried but deliberate swipe outright) with at most 50 px of vertical drift at any point: `touchmove` cancels it mid-gesture rather than only at the lift. Two more rules came from walking the sequences: a touch that starts outside the terminal (a swipe over the home screen) resets the published axis, so a terminal scroll a moment earlier cannot veto it, and a lift the terminal consumed (`defaultPrevented`: its long-press selection gesture, which on blank space leaves no selection behind to check) is never a swipe; the second-finger cancel stays set until the next touchstart, so the first finger lifting cannot clear it.
+
+Tests: `test/terminal-touch-tap.test.ts`, `test/session-swipe-gesture.test.ts` (the real `SwipeHandler` and the terminal's axis lock), `test/mobile/tabs.test.ts` (CDP swipes, mobile suite).
 
 ### Entrance animations