docs(licence): record GitHub single-display resolution (Addendum A8) (#447)

## Context

The estate licence policy (Rule 1) splits per-file SPDX two ways —
`MPL-2.0` for code, `CC-BY-SA-4.0` for prose. GitHub, however, surfaces
only **one** repo-level licence (licensee-detected from the root
`LICENSE`). The owner resolved that single displayed licence to
**MPL-2.0** while keeping both licence texts present in every repo. That
rationale was implicit in the canon but never explicitly recorded; this
PR captures it.

## Change

Additive only — **Rules 1–3 are unchanged and no per-file licence header
is modified** (respecting Addendum A2's "manual, per-file, owner-only"
rule for header remediation).

- `LICENCE-POLICY.adoc` — new **Addendum A8** documenting: root
`LICENSE` = MPL-2.0 text (drives GitHub's detected licence), both
`LICENSES/MPL-2.0.txt` + `LICENSES/CC-BY-SA-4.0.txt` present, prose
stays CC-BY-SA-4.0 via per-file SPDX header (not a second root licence).
Notes the separate-`LICENSE-docs` pattern a few repos use as an
acceptable equivalent.
- `.machine_readable/licensing-policy.toml` — mirrors A8 as a
`[github_display]` block (the machine-enforced mirror; kept in sync with
the `.adoc` source of truth).

## Why this is in-bounds

This is *authoring* a clarifying, dated addendum that reflects the
owner's 2026-07-01 statement — not a licence sweep or a header rewrite.
It records why the root `LICENSE` is MPL-2.0 rather than dual.

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

---
_Generated by [Claude
Code](https://claude.ai/code/session_012MpYSh6Wy8YMBH2E3qVyT7)_

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

Author: hyperpolymath

.machine_readable/licensing-policy.toml

@@ -22,6 +22,14 @@ meaning = "Creative Commons Attribution-ShareAlike 4.0 International"
 scope = "narrative documentation (*.adoc, *.md) in sole-owner repos"
 status = "owner ruling 2026-06-04 — docs are CC-BY-SA-4.0; code stays MPL-2.0"
 
+[github_display]                         # Addendum A8 (2026-07-01)
+resolved_to = "MPL-2.0"
+reason = "GitHub surfaces only one repo licence (licensee-detected from root LICENSE). Rule 1's per-file MPL/CC-BY split cannot be shown at repo level, so the single displayed licence is resolved to MPL-2.0."
+root_license = "MPL-2.0 text (drives GitHub's detected licence badge)"
+both_texts_present = ["LICENSES/MPL-2.0.txt", "LICENSES/CC-BY-SA-4.0.txt"]
+prose_licence = "CC-BY-SA-4.0 declared per-file (SPDX header) + LICENSES/CC-BY-SA-4.0.txt; NOT via a second root licence file"
+note = "display resolution, not relicensing; Rule 1 unchanged"
+
 [palimpsest_carveout]                    # Rule 2 — narrow, NOT the default
 spdx = "PMPL-1.0-or-later"
 applies = "EXACTLY three repos: palimpsest-license, palimpsest-plasma, consent-aware-http (the last prospectively)"

LICENCE-POLICY.adoc

@@ -244,6 +244,31 @@ audited and tightened. Genuine contradiction §C-C4 (zotero-voyant-export
 `ECHIDNA_ARCHITECTURE_UPDATE_3LANG.md`) is **not** on this list — it is
 a real defect tracked for an owner-directed single-file fix.
 
+=== A8 — GitHub single-licence display resolved to MPL-2.0 (2026-07-01)
+
+GitHub surfaces only *one* repository licence — the one its licensee
+detector reads from the root `LICENSE` file. Rule 1 splits per-file SPDX
+two ways (MPL-2.0 for code, CC-BY-SA-4.0 for prose), which GitHub cannot
+represent at the repo level. The estate therefore resolves the single
+GitHub-displayed licence to **MPL-2.0**: every repo's root `LICENSE`
+carries the MPL-2.0 text, so the GitHub sidebar shows `MPL-2.0`. Both
+canonical texts remain present in every repo — `LICENSES/MPL-2.0.txt`
+and `LICENSES/CC-BY-SA-4.0.txt` (REUSE-style) — and prose stays
+CC-BY-SA-4.0 by its per-file SPDX header. This is a *display resolution,
+not a relicensing*; Rule 1 is unchanged.
+
+Mechanical consequences (what every repo ships):
+
+* Root `LICENSE` = MPL-2.0 text (drives GitHub's detected licence).
+* `LICENSES/` carries *both* `MPL-2.0.txt` and `CC-BY-SA-4.0.txt`.
+* Prose files declare CC-BY-SA-4.0 via their own SPDX header plus the
+  `LICENSES/CC-BY-SA-4.0.txt` text — not via a second root licence file.
+
+A separate `LICENSE-docs` (CC-BY-SA-4.0) file, as a few repos ship, is an
+acceptable equivalent for surfacing the prose licence, but the `LICENSES/`
+REUSE directory is the canonical carrier and the root `LICENSE` stays
+MPL-2.0 so the single GitHub display resolves as above.
+
 == See Also
 
 * `PALIMPSEST.adoc` (this directory) — full narrative