S24.25: "Tier" means three different things, one of them contractual #682

Parent epic: #254

Purpose

Three separate axes in this repository are called tiers, and two of them use the
bare token "Tier 1" to mean incompatible things.

The support axis is contractual. SECURITY.md binds it to CVE treatment, signed
releases and SBOM entries, and SECURITY.md, SUPPORT.md and CONTRIBUTING.md
tie it to the free-versus-commercial licence split. A reader who meets "Tier 1"
without a qualifier cannot tell which axis is meant, and one of the readings is a
commitment to a paying integrator.

The repository already relies on qualification to stay safe —
docs/misra-deviations.md says "the Tier 1 naming scheme in
docs/NAMING.md" at every mention. That convention is undocumented and holds
only while every author remembers it.

Agreed

• Exactly one axis keeps the numbered "Tier N" form. The other two are renamed to
  terms that cannot be confused with it.
• Whichever axis is renamed, SECURITY.md, SUPPORT.md and CONTRIBUTING.md
  keep saying precisely what they say today about support and licensing. No
  wording change may narrow or widen a stated commitment.

Open — settle when the story is picked up

• Which axis renames. The support axis has the fewest call sites but the highest
  cost of error, being customer-facing and licence-linked. The naming axis has
  more call sites (docs/NAMING.md throughout, .coderabbit.yaml, SKILL.md,
  docs/README.md, docs/porting.md, docs/misra-deviations.md x6) but is
  entirely internal-facing.
• Whether the MISRA rigour axis (Strict / Pragmatic / Consistency-only) is
  already safe by being named rather than numbered, or should stop being called a
  tier at all.
• docs/NAMING.md:80 still heads its section ## Tier 1 — External linkage (public API). The (public API) parenthetical is the root cause of the whole
  confusion: it equates external linkage with public API. Dropping it is the one
  concrete edit already identified, and is cheap regardless of which way the
  rename decision goes.

Scope re-cut, 2026-08-17

Audited against the tree during the pre-0.1.0 issue review. Two of the four
findings originally rolled in here have moved on, and the mechanical remainder is
carved out so this story is a decision rather than a mixed bag.

Resolved differently than proposed. This story recommended deleting the
docs/NAMING.md paragraph that asserted two library-internal classes are Tier 1.
It was instead rewritten and is now correct: NAMING.md:137-146 explains that
Tier 1 is decided by linkage rather than audience, names SolidSyslogRecordStore
and SolidSyslogBlockSequence as the two cases, and gives the Path B
symbol-collision reason. Better than deletion. Only the section heading is left,
recorded above.

Stale finding, struck. This story claimed .coderabbit.yaml's citation of
BlockSequence.c::ScanForExistingBlocks was dead after the S33.04 rename.
BlockSequence_ScanForExistingBlocks exists at
Core/Source/SolidSyslogBlockSequence.c:141. The citation is loose on the
filename prefix; it is not the broken reference it was raised as.

Carved out to a chore, and delivered. The .coderabbit.yaml resync and the
stale-path CI gate were mechanical, carried no contractual risk, and did not need
this story's decision first. #773 landed all of it: .coderabbit.yaml's Tier 1
wording now states linkage rather than "public functions", the outX rule the
S23.22 audit deleted from NAMING.md is gone from the review config too, build
files have a path_instructions entry where they previously matched none, and
scripts/check_references.py asserts that a repo-relative path quoted in a .md,
.yaml or CMake file resolves.

That gate is structured so #740 — the same assertion for symbols rather than paths
— extends it rather than growing a second script; the seam is named in the script.

What is left on this story is the terminology decision alone, plus the
(public API) parenthetical recorded above. No mechanical work remains.

Acceptance

• "Tier 1" resolves to exactly one meaning wherever it appears unqualified, and
  no document states or implies that a library-internal class carries a support
  or security commitment.
• SECURITY.md, SUPPORT.md and CONTRIBUTING.md state the same support and
  licensing commitments after the change as before.