docs: convert tech-debt audit to AsciiDoc (last Estate Rules blocker) (#25)

Estate Rules stayed red on `main` after the CI-blocker PRs merged. The
failing step was **AsciiDoc-by-default**, on one file:
`docs/tech-debt-2026-05-26.md`.

Converted to `.adoc` rather than allowlisted — it is ordinary
documentation, so the estate rule applies with no justification
available. Content preserved verbatim; only markup changed.

**Verified locally on main:**
```
check-no-md-in-docs.sh  clean -> exit 0   with probe .md -> exit 1
check-root-shape.sh     clean -> exit 0
```
Gate red-teamed both directions, so this is not a fake pass.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

Author: hyperpolymath

docs/tech-debt-2026-05-26.adoc

@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: CC-BY-SA-4.0
+// Copyright (c) Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
+= Tech-Debt Audit — rsr-template-repo — 2026-05-26
+
+*Source:* estate-wide automated scan 2026-05-26.
+*Companion:* https://github.com/hyperpolymath/standards/tree/main/docs/audits[`hyperpolymath/standards` 2026-05-26-estate-*-debt audits].
+*Combined severity:* `LOW`.
+
+This file records the *raw findings* — it does not by itself fix the debt. Each section ends with a 'Recommended next move' line; closing the debt is follow-up work.
+
+== 1. Proof debt
+
+Scanner counted the following markers in proof-bearing files of this repo:
+
+----
+files=   13 | Coq-Axm/Adm=   0 | Lean-srry/ax=   0 | Agda-pst=   0 | Idr-blv=   6 | Idr-prtl=   0 | Fstr-asm=  0 | TODO=  0 | Unsafe=  0
+----
+
+*Total markers:* 6. *Severity:* `>06`.
+
+*Marker types* (any non-zero counts above):
+* Coq `Axiom`/`Admitted` — unconditional proof escapes.
+* Lean `sorry`/`axiom` — Lean's equivalent.
+* Agda `postulate` — accepted axiomatically.
+* Idris2 `believe_me`/`assert_total` — runtime-safe coercion / totality assumption.
+* Idris2 top-level `partial` — totality-check waived.
+* F\* `assume val`/`admit_p` — F\* admit.
+* `TODO PROOF` / `OWED:` — self-documented debt markers.
+* `unsafePerformIO`/`unsafeCoerce` — soundness-relevant escape hatches in Haskell/Rust source.
+
+*Recommended next move:* triage each finding into one of: (a) discharge by proof, (b) cover with property-tests + a documented refutation budget, or (c) annotate as a known/necessary axiom (e.g. `funExt`) in `docs/proof-debt.md`.
+
+== 2. Licence debt
+
+[cols="1,1",options="header"]
+|===
+|Field |Value 
+|LICENSE file |`LICENSE` 
+|SPDX header |`MPL-2.0` 
+|Manifest licence |`NONE` 
+|Body classifier |`Palimp-MPL-2.0` 
+|Severity |`ok` 
+|===
+
+
+*Recommended next move:* none for licence.
+
+== 3. Documentation debt
+
+[cols="1,1",options="header"]
+|===
+|Field |Value 
+|README lines |186 
+|`docs/` files |70 
+|`docs/` LoC |4218 
+|CHANGELOG.md |Y 
+|CONTRIBUTING.md |N 
+|CODE_OF_CONDUCT.md |N 
+|SECURITY.md |N 
+|Severity |`OK` 
+|===
+
+
+*Recommended next move:* none for docs.
+
+== Cross-references
+
+* Estate proof-debt audit: `hyperpolymath/standards/docs/audits/2026-05-26-estate-proof-debt.md`
+* Estate licence-debt audit: `hyperpolymath/standards/docs/audits/2026-05-26-estate-licence-debt.md`
+* Estate documentation-debt audit: `hyperpolymath/standards/docs/audits/2026-05-26-estate-documentation-debt.md`
+
+'''
+
+🤖 Generated by Claude Code estate-wide tech-debt scan (2026-05-26). This file is informational — closing the debt is follow-up work owned by the maintainer.