Stated the compiler and coverage requirements directly, and said who the pinned toolchain default serves (#718)

* Stated the compiler and coverage requirements instead of citing a file no contributor can open

Seven comments across five files cited a maintainer-local document as the
source for two project requirements: that GCC 14 on Linux is the default
compiler, and that the coverage target is 100%. That document is not part of
this repository and is not published anywhere, so the citation gave a reader
nothing to follow -- it named a source they cannot open, in place of simply
stating the requirement.

Both requirements are real and both stay. Only the pointer goes: each comment
now states the requirement on its own terms, which is what the surrounding
prose was already doing everywhere else.

  cmake/cortex_r52.cmake                     the pinned reference toolchain
  scripts/check_gcc.sh                       why the script exists
  .github/workflows/gcc_check.yml            why the workflow exists, and the
                                             GCC_VERSION pin
  .github/workflows/r52_fvp.yml              the GCC_VERSION pin
  .github/workflows/regression_template.yml  the coverage floor, twice

Comments only; no behaviour changes. Two paragraphs are rewrapped where the
shorter text left a ragged line. Verified that scripts/check_gcc.sh still
parses and prints its help from the header range it slices, and that
cmake/cortex_r52.cmake still configures the Cortex-R52 build.

Assisted-by: Claude Code (Opus 5) <noreply@anthropic.com>

* Said who the pinned toolchain default in the CMake toolchain files serves

Both cmake/cortex_r52.cmake and cmake/cortex_m52.cmake default
ARM_TOOLCHAIN_PATH to a toolchains directory under the user's home, guarded by
an EXISTS check. Nothing said whether CI relies on that, and the natural
reading is that it does.

It does not. The three workflows that install a toolchain unpack it into the
workspace and cache it there, and r52_fvp.yml puts that directory on PATH
before configuring; scripts/check_gcc.sh passes -DARM_TOOLCHAIN_PATH at each of
its three CMake call sites. On a runner the guarded directory is absent, the
EXISTS check falls through, and the compiler comes from PATH. The default only
ever fires on a developer machine, where it is what makes a no-flag build work.

Both comments now say that, so the default is not mistaken for a CI dependency
and not removed as dead code. cortex_r52.cmake carries the explanation and
cortex_m52.cmake refers to it, matching the cross-reference already there.

The r52 comment also claimed absolute paths mean "the build does not depend on
PATH ordering", which is only true where the pinned directory exists -- in CI
the build depends on PATH and nothing else. Qualified accordingly.

Comments only; no behaviour changes. Verified that both toolchain files still
configure, and that the fall-through is real: with HOME pointed at a directory
holding no toolchains, cortex_r52.cmake configures against the arm-none-eabi-gcc
found on PATH.

Assisted-by: Claude Code (Opus 5) <noreply@anthropic.com>

.github/workflows/gcc_check.yml

@@ -7,11 +7,11 @@ name: gcc_check
 # link the example builds, both the script-driven ones and those driven by
 # CMake.
 #
-# Why this exists: GCC is the project's declared default compiler (AGENTS.md,
-# "The default compiler for the project is GCC 14 on Linux") and until this
-# workflow landed, nothing in CI compiled a line of any port with it. The only
-# cross-compilation check that ran was clang_check, so the LLVM path was better
-# guarded than the GNU one, on ports whose directory is literally named gnu.
+# Why this exists: GCC 14 on Linux is the project's default compiler, it is
+# what the gnu ports exist for, and until this workflow landed, nothing in CI
+# compiled a line of any port with it. The only cross-compilation check that
+# ran was clang_check, so the LLVM path was better guarded than the GNU one,
+# on ports whose directory is literally named gnu.
 #
 # What it covers: 840 assembly sources across 40 port families, 469 of them
 # again behind feature macros, common/src for nine cores, 302 module manager C
@@ -94,8 +94,8 @@ jobs:
     env:
       # Pinned deliberately, as the runner image is: a toolchain upgrade should
       # be a reviewable commit rather than something that changes underneath the
-      # ports. 14.3.rel1 matches AGENTS.md's GCC 14 default and the version
-      # cortex_m already pins.
+      # ports. 14.3.rel1 is the GCC 14 the project builds against, and the
+      # version cortex_m already pins.
       # Releases: https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
       GCC_VERSION: 14.3.rel1
 

.github/workflows/r52_fvp.yml

@@ -75,7 +75,7 @@ jobs:
       # Pinned deliberately. Matches gcc_check.yml and ci_cortex_m.yml so all
       # three share one cache entry rather than each holding its own copy of
       # the same archive; change them together or the sharing silently stops.
-      # 14.3.rel1 is AGENTS.md's declared GCC 14 default.
+      # 14.3.rel1 is the project's GCC 14 default.
       GCC_VERSION: 14.3.rel1
 
       # Where the Armv8-R AEM FVP comes from.

.github/workflows/regression_template.yml

@@ -54,7 +54,7 @@ on:
       # rate, and not the lower of the two. Probed on the same run: the
       # ThreadX report at 100.00% lines and 77.67% branches passes a floor of
       # 99. Worth knowing, because branch coverage is around 78% in both
-      # suites while AGENTS.md asks for 100%, and a floor set from the
+      # suites while the project asks for 100%, and a floor set from the
       # headline line figure says nothing about it.
       #
       # Each suite sets its own in regression_test.yml, because they do not
@@ -157,9 +157,9 @@ jobs:
     # ! opens a YAML tag, and the expression will not parse without it.
     #
     # fail_below_min turns the summary into a gate. Until now coverage could
-    # fall from any figure to any other and no check went red, against an
-    # AGENTS.md that asks for 100% -- a stated requirement measured with a
-    # gauge that could not fail.
+    # fall from any figure to any other and no check went red, against a
+    # project target of 100% -- a stated requirement measured with a gauge
+    # that could not fail.
     #
     # One thing the floor does not defend, and it is the likeliest way for
     # coverage to break: an empty report reads as 100%. gcovr writes