v1.6 — full-profile tasking deadlock fixed; CI gate; ACATS re-validated

Important

If you use the full runtime profile, upgrade from v1.5.
On v1.5 the full profile deadlocks any program whose environment task waits
for dependent tasks — including this repository's own
esp32s3_full_tasking example, which stops after one worker iteration.

The boot CPU's idle ATCB self-linked System.Tasking.All_Tasks_List, so
Vulnerable_Complete_Master walked a list that never terminates while
holding the global RTS lock, freezing every task. The environment task's own
delay kept working (it was the one spinning), so it presented as
"library-level and dynamically-allocated tasks never wake" rather than an
obvious hang. light-tasking and embedded are unaffected.

Compatibility — three changes that can affect an existing setup

1. HAL sources moved into src/{peripherals,devices,net,text_io}/.
   Unit names are unchanged, so with ESP32S3.SPI; still works — but anything
   using libs/esp32s3_hal/src as a flat search path breaks. Use src/**.
2. Toolchain resolution changed. tools/sdk-env.sh now prefers the recorded
   known-good version over the newest installed. No effect if you have the
   validated set; it changes which compiler builds your firmware if you don't.
3. libs/esp32s3_wifi/esp32s3_wifi.gpr now declares Target, Runtime and a
   per-profile object directory. It previously only worked when built from
   inside an example.

Highlights

• CI. .github/workflows/ci.yml runs ./x test on every push — host suites,
  every library on every profile it supports (warnings are failures), and a
  build of all 96 examples. Nothing built the code before; it immediately caught
  an example that had not compiled in six weeks, and a HAL that would not build
  under its own default profile.
• HAL profile scoping by source directory, replacing a ~130-entry exclusion
  list that had drifted. Adding a driver now defaults to safe.
• HAL and libs/tls build clean under -gnatwa — ~110 real warnings fixed.
• TLS: a short write no longer truncates a record silently; Socket_Error no
  longer escapes the library as a board reset; and a zero-length
  application_data record (legal per RFC 8446 §5.1) no longer raises
  Constraint_Error out of Recv.
• SPARK: GPIO's lock-free pad operations proved; register banks carry explicit
  external-state aspects.
• Docs: the guide's prose moved out of build.py (6,047 → 1,253 lines, output
  byte-identical), and a README for the 36 examples that had none.

Conformance

ACATS 4.2 re-run on real hardware across all three profiles against this tree:
zero regressions, three improvements, and zero port-specific defects.

profile	applicable	passed
light-tasking	1132	674
embedded	1257	884
full	1559	908

Full report: Ada_esp32s3_acats/ACATS_RESULTS.md

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What's Changed

• Build the code in CI, and fix what that turned up by @rowsail in #206
• rts: fix the full-profile idle-ATCB deadlock (found by ACATS on hardware) by @rowsail in #207
• docs: bring the SDK's own ACATS figures up to date by @rowsail in #208

Full Changelog: v1.5...v1.6