Expand platform support and distribution readiness

[TheusHen]

What changed

This closes the software-only readiness gaps identified after v0.2.0:

• adds RV64 retained capture and a complete-or-unavailable CPU64 LEP extension;
• adds host-tested reset-reason integration boundaries for Nordic, NXP, Microchip SAM, TI and Silicon Labs;
• adds a bounded Linux fatal-signal handoff and a normal-runtime POSIX file backend;
• adds a dependency-free latch-dump JSON/text decoder for binary, stdin and bounded hexadecimal input;
• adds Arduino/PlatformIO and ESP-IDF Component Manager packaging, cooperative ESP32 and AVR examples, and installed CMake consumers;
• adds an AVR-oriented constrained profile and fixes two real 16-bit portability defects in Poly1305 and stream length framing;
• publishes reproducible footprint tooling and measured Cortex-M4/Arduino Mega baselines;
• synchronizes release metadata and documents the v0.3.0 preparation/tag/registry procedure;
• documents exact qualification, crypto-audit and MISRA boundaries instead of implying unsupported guarantees.

The Linux signal handler intentionally performs only one fixed-size nonblocking pipe/FIFO write and then _exit; LEP encoding, storage and retry work remain outside signal context.

Validation

• Linux/GCC: 41/41 tests
• ASan + UBSan: 39/39 tests
• Windows/MSVC: 40/40 tests
• packaged CMake consumers: C, C++, Nordic port and Linux port
• Arduino Mega 2560 package compile/link with AVR GCC 7.3 and shift-overflow warnings promoted to errors
• AVR footprint: 34,554 B Flash and 2,416 B static RAM
• Rust: fmt, Clippy, 7 tests, ARM/RISC-V no_std checks, package and publish dry-run
• release metadata, documentation links, embedded package layout, LEP vectors, source minification and actionlint
• coverage spot checks: new vendor adapters 100%; common reset mapper 100%; Poly1305 98.15%; POSIX file backend 91.41%

The local PlatformIO ESP32 download could not complete because the workstation ran out of disk space while installing the toolchain. The PR workflow installs it in a clean runner and validates the packed artifact.

Evidence boundaries

• New vendor ports, RV64, Linux and AVR paths are not hardware-tested in this change.
• The existing ESP32-D0WD-V3 / ESP-IDF 5.5.0 fixture remains the only qualified capture -> reboot -> recovery -> durable ACK path.
• No independent cryptographic audit or MISRA certification is claimed.
• PlatformIO, crates.io, Arduino and ESP-IDF registries are prepared but have not been published.
• No release tag is created by this PR.

Qualification, stress, LTS and reference-design follow-up

• adds a public hardware compatibility matrix generated from validated JSON evidence; only the dated ESP32 fixture is marked physically qualified, with its limited scope explicit;
• adds QEMU Cortex-M fault entry tests using the production assembly entry and Renode RV32 illegal-instruction trap injection;
• expands physical HIL entry points with HardFault and stack-canary scenarios without presenting emulator evidence as hardware qualification;
• adds deterministic spool stress across every committed-envelope byte, 160 interrupted/partial-write cases and recovery past a corrupt record;
• adds CI-executed OTA rollback, encrypted/redacted critical-system and low-power/deep-sleep reference designs;
• defines objective 1.0/LTS gates, stable branch/backport policy, external-audit scope, publication policy and report template.

Follow-up validation on the current commit:

• hosted GCC build and 45/45 tests passed;
• all three reference designs passed;
• qualification-matrix validation, documentation links, LEP vectors, package metadata and clang-format passed;
• QEMU/Renode jobs run in GitHub Actions with pinned inputs and remain non-HIL evidence.

No external audit was claimed or fabricated, no stable branch was created, and no hardware row was promoted without physical evidence.

[codecov]

Codecov Report

❌ Patch coverage is 82.57956% with 104 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
ports/embedded-linux/file_backend.c	73.22%	16 Missing and 33 partials ⚠️
src/capture/capture.c	82.85%	14 Missing and 10 partials ⚠️
arch/linux/linux.c	71.42%	7 Missing and 9 partials ⚠️
src/envelope/lep.c	68.42%	2 Missing and 10 partials ⚠️
src/transport/stream.c	62.50%	1 Missing and 2 partials ⚠️

📢 Thoughts on this report? Let us know!