fix(deps): pin lora-phy to swaits/lora-rs#fixed for sx127x/sx126x reliability

Switch lora-phy from crates.io to the swaits/lora-rs "fixed" branch
which carries three fixes awaiting upstream PR acceptance:

  - phy: sx127x: clear stale IRQ flags before reconfiguring DIO mapping
    in set_irq_params (fix/sx127x-irq-clear-position)
  - phy: sx127x: clear stale IRQ flags in do_rx before mode change
    (fix/sx127x-rx-irq-clear)
  - phy: sx126x: pre-command BUSY check + standby/IRQ-clear hygiene
    around CAD (fix/sx126x-busy-race)

Validates TBeam classic (sx127x) in particular and tightens reliability
across every board (the sx126x BUSY-race fix lands on every nRF/RP2040
board too). Pinned to commit e8a52ebd via Cargo.lock; revert to
crates.io once the three PRs land upstream.

TODO.md

@@ -1,30 +1,39 @@
 # Firmware TODO List
 
-## `lora-phy` fix: drop fork pin once PR #428 merges + releases
+## `lora-phy` fix: drop fork pin once PRs #428 / #431 / #432 merge + release
+
+Upstream PRs (all open):
+
+- [#428 — *phy: add pre-command BUSY checks per Semtech
+  datasheets*](https://github.com/lora-rs/lora-rs/pull/428) (sx126x):
+  pre-command BUSY check + standby/IRQ-clear hygiene around CAD.
+- [#431 — *phy: sx127x: clear stale IRQ flags in do_rx before mode
+  change*](https://github.com/lora-rs/lora-rs/pull/431).
+- [#432 — *phy: sx127x: clear stale IRQ flags before reconfiguring DIO
+  mapping in set_irq_params*](https://github.com/lora-rs/lora-rs/pull/432).
 
-Upstream PR: [lora-rs/lora-rs#428 — *phy: add pre-command BUSY checks
-per Semtech datasheets*](https://github.com/lora-rs/lora-rs/pull/428)
-(open).
 Fork branch we ship from:
-[`swaits/lora-rs @ fix/sx126x-busy-race`](https://github.com/swaits/lora-rs/tree/fix/sx126x-busy-race).
+[`swaits/lora-rs @ fixed`](https://github.com/swaits/lora-rs/tree/fixed)
+— a merge of all three fix branches kept up-to-date with upstream
+`main`.
 
-Firmware consumes the fix via a direct `git` dependency in
+Firmware consumes the fixes via a direct `git` dependency in
 `Cargo.toml`:
 
 ```toml
-lora-phy = { git = "https://github.com/swaits/lora-rs.git", branch = "fix/sx126x-busy-race", features = ["defmt-03"] }
+lora-phy = { git = "https://github.com/swaits/lora-rs.git", branch = "fixed", features = ["defmt-03"] }
 ```
 
-When PR #428 merges and a `lora-phy` release ships on crates.io that
-contains it, switch this line back to a normal `lora-phy = "X.Y"`
-crates.io version and drop the explanatory comment block above it.
+When all three PRs merge and a `lora-phy` release ships on crates.io
+that contains them, switch this line back to a normal
+`lora-phy = "X.Y"` crates.io version and drop the explanatory comment
+block above it.
 
-Hardware-verified on Wio Tracker L1: 20/20 clean-boot TX after the fix
-(vs ~50% before). The fix adds a pre-command BUSY check before each
-`SpiInterface` read/write op, keeping the existing post-command wait
-in place — belt-and-suspenders bracketing that closes the
-BUSY-assertion latency window (T_SW ≤ 600 ns) a single level-poll can
-miss.
+Hardware impact: large stability gain on every board — the sx126x
+BUSY-race fix lands on every nRF/RP2040 board, and the sx127x IRQ-clear
+fixes unblock TBeam classic in particular. Hardware-verified on Wio
+Tracker L1 (sx126x): 20/20 clean-boot TX after the fix (vs ~50%
+before).
 
 ---