docs: add the canon — routable architecture docs, a requirements register, and a drift report

[adbarc92]

Adds docs/canon/ — 21 files stamped at 7420d69 giving reqdrive a routable
documentation layer and, more importantly, a written record of where the code
and its requirements disagree.

Documentation only. No code changed, no behavior changed.

What is here

Layer	Files	What it does
Spine	architecture.md, index.json	path-glob routing table from any file to the doc that governs it; the machine-readable form for agent context
Modules	modules/*.md (9)	one per path partition — public surface with file:line anchors, invariants, requirement coverage
Conventions	conventions/*.md (4)	the cross-cutting rules no single module owns
Requirements	requirements/register.md, requirements/drift-report.md	602 requirements from 5 canonical sources; where the code contradicts them
Claims	claims-audit.md	what the project says about itself, graded against the above

Requirements are treated as canon throughout: where code contradicts a
requirement, the requirement is recorded as intended and the divergence goes in
the drift report. Documenting drift changed no code.

What the audit found

602 requirements · 517 satisfied · 48 drifted · 8 defects no requirement
covers · 0 real gaps (the 6 unimplemented reqs are all Tier-3 roadmap).
Every drift entry carries an adversarial verifier verdict; 3 candidate findings
were refuted during verification and are recorded so they are not re-raised.

The most consequential finding is DES-002: the fail-closed draft-PR gate is
fail-open four ways. The gate shape is right, but three of its inputs can
report success without success occurring — an unreadable prd.json scores as
complete (every jq in verify_collect ends || echo "0", so "cannot count"
reads as "zero remaining"), an empty story list scores as complete, agent
story-deletion scores as complete, and a blank or commented-out testCommand
reads as a pass. Two independent verifiers reproduced non-draft PRs with real
incomplete work using the repo's own pipeline harness. This matters because the
L2/L3 readiness claim in docs/STATUS.md rests on it.

Also worth flagging: run.json.pr_url holds a two-line string rather than a URL
(one missing >&2 at lib/pr-create.sh:95), the PR body's "Stories completed"
line has no .passes filter and contradicts its own verification table, and a
glob in riskTiers silently matches nothing while validate reports PASSED.

Nine canon-vs-canon conflicts are recorded in the register — including the test
count, where CLAUDE.md says 152 and 157 and the measured figure is 202.

Commits

Four, ordered so each commit's internal links resolve:

1. docs(canon) — requirements register and drift report
2. docs(canon) — claims audit
3. docs(canon) — module and convention docs
4. docs(canon) — index and architecture spine

Verification

No CI job reads docs/; all six gates run against bin/, lib/, install.sh
and tests/, none of which this branch touches, so this branch cannot move any
gate. The suite is running against this commit; the result is posted as a comment
below.

Follow-ups this does not do

The drift report is a record, not a fix. The fix list is ordered by severity at
the top of drift-report.md; DES-002 is four bounded changes and is the one
worth doing first.