chore(spdx): migrate PMPL-1.0-or-later → MPL-2.0 (20 files) (#54)

## Summary

The repo's LICENSE file is canonical **MPL-2.0** (migrated in
absolute-zero#42 alongside the wrapper-conversion sweep). But 20 files
across the repo still carried the legacy `PMPL-1.0-or-later` SPDX
header.

Per estate language policy
([`feedback_estate_lang_policy_2026_05_25`](../../README.md#license)):
`PMPL-1.0/MPL-1.0 → MPL-2.0`. This PR brings the headers in line with
the LICENSE.

## Files touched (all mechanical)

- 3 root .adoc: `AUDIT.adoc`, `ROADMAP.adoc`, `RSR_COMPLIANCE.adoc`
- 12 `docs/wiki/*.md`
- 3 `*/README.adoc` (tests, tools, verification)
- 2 `docs/archive/*.adoc`

## Verification

Post-merge `grep -rl 'PMPL-1.0-or-later'` returns 0 hits outside of git
history.

Author: hyperpolymath

AUDIT.adoc

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: PMPL-1.0-or-later
+// SPDX-License-Identifier: MPL-2.0
 = Absolute Zero — Audit Trail
 Jonathan D. A. Jewell <developer@joshuajewell.dev>
 :toc:

ROADMAP.adoc

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: PMPL-1.0-or-later
+// SPDX-License-Identifier: MPL-2.0
 = Absolute Zero: Roadmap to v12.0
 Jonathan D. A. Jewell <jonathan.jewell@open.ac.uk>
 :toc: left

RSR_COMPLIANCE.adoc

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: PMPL-1.0-or-later
+// SPDX-License-Identifier: MPL-2.0
 = Absolute Zero — Rhodium Standard Repository (RSR) Compliance
 Jonathan D. A. Jewell <developer@joshuajewell.dev>
 :toc:

docs/archive/ROADMAP-2026-02-05.adoc

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: PMPL-1.0-or-later
+// SPDX-License-Identifier: MPL-2.0
 = Absolute Zero Roadmap
 Jonathan D. A. Jewell <jonathan.jewell@open.ac.uk>
 :toc:

docs/archive/SESSION-2026-05-25-HANDOFF.adoc

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: PMPL-1.0-or-later
+// SPDX-License-Identifier: MPL-2.0
 = Session Handoff — 2026-05-25 Repo Tidy
 Claude (session 7927557c-2938-4d53-b987-a6f8ebc44611)
 :toc:

docs/wiki/ABI.md

@@ -1,4 +1,4 @@
-<!-- SPDX-License-Identifier: PMPL-1.0-or-later -->
+<!-- SPDX-License-Identifier: MPL-2.0 -->
 # ABI
 
 The Idris2 ABI surface at `src/abi/` declares the FFI boundary that the

docs/wiki/Architecture.md

@@ -1,4 +1,4 @@
-<!-- SPDX-License-Identifier: PMPL-1.0-or-later -->
+<!-- SPDX-License-Identifier: MPL-2.0 -->
 # Architecture
 
 Three layers, loosely coupled.

docs/wiki/Audit-Trail.md

@@ -1,4 +1,4 @@
-<!-- SPDX-License-Identifier: PMPL-1.0-or-later -->
+<!-- SPDX-License-Identifier: MPL-2.0 -->
 # Audit Trail
 
 Short summary; the authoritative ledger is [`AUDIT.adoc`](../../AUDIT.adoc).

docs/wiki/Contributing.md

@@ -1,4 +1,4 @@
-<!-- SPDX-License-Identifier: PMPL-1.0-or-later -->
+<!-- SPDX-License-Identifier: MPL-2.0 -->
 # Contributing
 
 Short summary; the authoritative version is [`CONTRIBUTING.adoc`](../../CONTRIBUTING.adoc) at the root.

docs/wiki/FAQ.md

@@ -1,4 +1,4 @@
-<!-- SPDX-License-Identifier: PMPL-1.0-or-later -->
+<!-- SPDX-License-Identifier: MPL-2.0 -->
 # FAQ
 
 ### Why prove that a program does nothing?