docs: clock tools + e-ink input handling; v1.21 release notes

- release-notes v1.21: add Clock tools (alarm/timer/stopwatch) to What's new,
  e-ink button responsiveness + double-tap debounce to Fixes, and the input
  edge-capture/key-queue and hardware-timer ringtone notes to Under the hood.
- README: note clock tools on the Clock Screen entries.
- solo_ui_framework: document the hardware->handleInput path (mandatory
  begin() per button, IRQ edge capture, key queue + coalesced redraw).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

release-notes.md

@@ -9,6 +9,7 @@
 - **Map & status-bar upgrades** — the home mini-map gains a **north marker** and a **scale tick**; the status line shows the tracked-node count and, with a fix, an **arrow + distance to the nearest tracked contact** (e.g. `Track:3 →120m`); a **GPS fix icon** sits in the top status bar (boxed once a fix is valid, plain while searching), shown only on GPS boards while **GPS** is enabled in Settings.
 - **Trail auto-pause** — recording **freezes on stops** (banking elapsed time and breaking the map line across the idle gap) and **resumes on movement** without ending the session; the home-screen blink keeps going while paused.
 - **Collapsible Tools** — tools are grouped into fold-in-place **Location / Comms / System** sections, the same model as Settings (Tools always opens folded to the section list), and the home carousel now uses **page-indicator icons** instead of dots.
+- **Clock tools — alarm, timer, stopwatch** — press **Enter** on the Clock page for three time utilities: a **one-shot wake alarm** (set hour/minute with the digit editor; a **bell** marks it on the clock face and the status bar while armed), a **countdown timer** (full **HH:MM:SS**, single-digit cursor), and a **stopwatch**. The alarm and timer **ring with a melody — overriding mute** — and are silenced by **any key**. They keep running with the display off or locked, and the alarm is scheduled as an **absolute instant** so it survives the clock re-syncs the mesh / app / GPS / CLI can trigger at any time (it can't wake the device from a full Shutdown, where the CPU is off).
 - **Waypoint coordinate editor** — add a waypoint by scroll-editing its latitude/longitude digit by digit.
 - **On-device room login with saved passwords** — log in to a room server straight from the device (no phone app): pick the room and the password prompt appears automatically (a blank password works for open rooms), or re-login any time via the room's **context-menu "Login…"**. The password is **remembered across reboots**, so a room you've used before logs back in without retyping; a failed login (e.g. the server's password changed) forgets the stale password so the next attempt prompts again. Room passwords entered via the **phone app** are saved on the device too, so it can post to that room standalone after a reboot. Saved passwords are written with the same atomic, crash-safe persistence as contacts and channels.
 
@@ -23,11 +24,14 @@
 - **GPS status icon** is hidden when GPS is turned off in Settings, instead of sitting there empty.
 - **Trail — start with GPS off** now prompts **"GPS is off — Enable GPS & start"** instead of silently starting a session that shows "Waiting for GPS fix" forever and records nothing.
 - Null-guarded the Locator target picker and clamped the loc-share channel index on load.
+- **e-ink button responsiveness** — joystick and Back presses are no longer dropped during a slow panel refresh. The directional buttons were never initialised for interrupt edge-capture (only the user button was), so they silently stayed on the polling path; now every button is initialised, and a burst of taps captured while the panel is refreshing replays as **discrete navigation steps** instead of collapsing into a single ignored multi-click. Edge capture and the live-pin self-heal are both debounced, so **contact bounce can't surface one press as a double-tap** (e.g. start+stop on the stopwatch).
 
 ### Under the hood
 
 - **Streaming trail simplification** — GPS points are simplified as they're recorded via a fixed-corridor (Reumann–Witkam) pass: straight runs collapse to their two endpoints while curves stay bounded to within the **Min dist** tolerance of the real track, so the 512-point buffer covers a far longer route than a flat point budget would suggest. The buffer is kept at 512 points to bound the static RAM footprint on nRF52.
 - A UITask-decoupled active-target resolver (`resolvePersonPos` / `activeTargetPos`) replaces the duplicated target-resolution logic that lived separately in the Locator, Navigate and Map entry points.
 - `-Os` size optimisation on the e-ink and GAT562 30S solo envs to keep them within the flash budget.
+- **Input edge-capture + key queue** — on e-ink, button edges are latched by a GPIO interrupt during the blocking `endFrame()` refresh and replayed once the loop runs again; `loop()` then drains the whole burst into a small key FIFO and applies every key before a **single** redraw. Rapid navigation neither gets lost nor costs one slow refresh per step. (Buttons fall back to polling automatically if no GPIOTE channel is free.)
+- **Ringtone player on a hardware timer** — note advance moved off the `loop()` poll onto an nRF52 TIMER1 compare interrupt, so a blocking e-ink refresh can no longer stretch or skip a note; alarm/timer melodies stay on tempo regardless of render cadence.
 
 > **Upgrade note:** if a previous version lost your contacts after a hang, you'll need to re-add them once — the atomic-save protection applies from this release onward.