Phase 2: Raspberry Pi Pico 2W (RP2350) support + guide

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Part of Phase 2 — Reach (ROADMAP.md).

The concrete demand signal for the freestanding profile (sibling issue): an embedded OSC endpoint on the Pico 2W (RP2350 + CYW43439 Wi-Fi), using the OscTap core with the Pico SDK + lwIP for transport.

Landed (branch claude/phase-2-prep-h8q9mz):

• docs/EMBEDDED_PICO2W.md — integration recipe: what to use from osc/ vs. replacing ip/ with lwIP UDP, the OSCTAP_FREESTANDING + exceptions trade-off (incl. the untrusted-input/DoS consideration), CMake glue, receive (lwIP udp_recv → ReceivedMessage) and send (OutboundPacketStream → pbuf) snippets, and a no-heap RT checklist.

Possible follow-ups (demand-driven):

• A buildable Pico SDK example sketch under examples/ (or a companion repo) compiled against arm-none-eabi-g++.
• Optional CI compile-check against the Pico SDK toolchain (weigh against the ROADMAP's "keep each phase green indefinitely" / standing-surface caution).
• Blocked on the non-throwing TryInit (sibling issue) for safely handling untrusted OSC traffic without exceptions.