feat: initial Xiao RP2040 mouse jiggler firmware

Embassy-based no_std firmware for the Seeed Studio Xiao RP2040 that
masquerades as a Dell MS116 USB HID Boot Mouse. Each cycle picks a
random axis from the RP2040 ROSC RANDOMBIT register, nudges +1 px,
dwells 25 ms, nudges -1 px, then sleeps 4.5 minutes. After 8 hours
elapsed from boot or RESET press the device idles silently (watchdog
still fed) until the user taps RESET (R) again, aligning a single
press with one workday.

Tooling:
- mise.toml pins rust 1.95.0 with explicit components and the
  thumbv6m-none-eabi target, plus cargo-binutils / uf2conv helpers.
- justfile shell is set to "mise exec -- sh -eu -c" so every recipe
  uses the pinned toolchain without any shell activation.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -0,0 +1,33 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+## [0.1.0] - 2026-04-27
+
+### Added
+
+- Initial Embassy-based `no_std` firmware for the Seeed Studio Xiao RP2040.
+- USB HID Boot Mouse, masquerading as a Dell MS116 (VID `0x413c`, PID `0x301a`).
+- Jiggle pattern: pick a random axis from the RP2040 ROSC `RANDOMBIT`, nudge
+  +1 px, dwell 25 ms, nudge −1 px, then sleep 4.5 minutes before the next
+  cycle.
+- 8-hour workday window after boot or `RESET (R)` press, then silent idle
+  (watchdog still fed) until the next manual reset.
+- 8-second hardware watchdog, fed in 5-second chunks during long sleeps.
+- `mise.toml` pinning rust 1.95.0 with explicit components
+  (`cargo`, `clippy`, `llvm-tools`, `rust-src`, `rust-std`, `rustc`,
+  `rustfmt`) and the `thumbv6m-none-eabi` target, plus cargo helpers
+  (`cargo-binutils`, `uf2conv`, `cargo-watch`, `cargo-bloat`,
+  `cargo-expand`).
+- `justfile` recipes for `build`, `release`, `check`, `clippy`, `fmt`,
+  `lint`, `ci`, `bin`, `uf2`, `flash`, `size`, `bloat`, `expand`, and
+  `bootstrap`. All recipes execute inside `mise exec -- sh -eu -c` so the
+  pinned toolchain is used regardless of shell activation state.
+
+[Unreleased]: https://github.com/swaits/jiggly/compare/v0.1.0...HEAD
+[0.1.0]: https://github.com/swaits/jiggly/releases/tag/v0.1.0