RFC: Android Kotlin → Rust/Tauri 2 migration

[hyperpolymath]

Status

DRAFT — RFC only. Awaiting owner review BEFORE any bulk conversion.
No Kotlin deleted, no Tauri scaffolding generated, no behaviour change.

Why

android/ ships 7 Kotlin files + 3 *.gradle.kts files, all banned by the
Hyperpolymath language policy. This keeps two CI gates permanently red:

• Check for Banned Languages (.github/workflows/language-policy.yml:87-94)
• governance / Language / package anti-pattern policy (estate-wide)

What this PR contains

A single document — docs/migrations/RFC-ANDROID-KOTLIN-TO-RUST.adoc — that:

1. Inventories every Kotlin component (LoC, role, replacement).
2. Names the unavoidable JVM-bytecode surface — Activity, Service,
   BroadcastReceiver, AppWidgetProvider — that Android instantiates by
   class name and that pure Rust cannot satisfy.
3. Proposes Path A (Tauri 2-generated Java shims under
   src-tauri/gen/android/, with a CI exemption analogous to
   node_modules/) and explicitly rejects Paths B (drop the widget) and
   C (JVM bytecode emission from Rust).
4. Lays out a 9-PR landing sequence with explicit dependencies.

Component mapping (one-line summary)

Kotlin file	Replacement
MainActivity.kt	Tauri 2 MainActivity + AffineScript webview UI
NeurophoneService.kt	Generated Java Service shim → JNI into Rust
BootReceiver.kt	Generated Java BroadcastReceiver shim → JNI
NativeLib.kt	Delete; lives in crates/neurophone-android/src/lib.rs
NeurophoneAppWidget.kt	Generated Java AppWidgetProvider shim
NeurophoneWidgetActions.kt	Generated Java BroadcastReceiver shim
NeurophoneWidgetConfigureActivity.kt	Generated Java Activity shim (or drop)
*.gradle.kts	Tauri-generated under gen/android/

Sub-PR sequence (proposed)

1. This PR — RFC only.
2. CI exemption for src-tauri/gen/android/ (coordinated with hyperpolymath/standards).
3. cargo tauri android init scaffolding.
4. Port NativeLib Kotlin → crates/neurophone-android/src/lib.rs.
5. Port NeurophoneService.
6. Port BootReceiver.
7. Port widget triple (provider / actions / configure).
8. AffineScript UI (replaces activity_main.xml).
9. Delete legacy android/ tree — both CI gates green.

PRs 2 & 3 sequenced; 4–7 parallelizable after 3; 8 needs 4; 9 gated on all.

Open questions for owner

1. Tauri vs Dioxus — RFC recommends Tauri 2; confirm.
2. CI exemption scope — OK to exempt src-tauri/gen/android/?
3. Estate governance — who owns the cross-repo anti-pattern policy
   callable in hyperpolymath/standards?
4. Widget config sacrifice — acceptable to drop the configure activity?
5. Hardware test plan — Oppo Reno 13 vs emulator + Termux?
6. SPDX clash — repo files use PMPL-1.0-or-later, local hook expects
   MPL-2.0. Pick canonical before sub-PRs.

Constraints honoured in this PR

• PMPL header attempted but blocked by local hook → MPL-2.0 used + clash
  flagged in the RFC's "Open questions". See open question chore(deps): update reqwest requirement from 0.11 to 0.12 #6.
• No new GitHub Actions added.
• No Deno/npm/TypeScript changes.

Test plan

• RFC document renders as AsciiDoc.
• Owner reviews component mapping for completeness.
• Owner picks Tauri vs Dioxus, confirms CI-exemption plan, resolves SPDX clash.
• Sub-PR Add STATE.scm project checkpoint file #2 (CI exemption) opens once approved.

🤖 Generated with Claude Code

[hyperpolymath]

Replaced by PR on chore/gossamer-migration-rfc — owner corrected the migration target from Tauri to Gossamer; rewriting under the right branch name.

[hyperpolymath]

Two owner decisions for this RFC are now settled — please update the doc accordingly before any sub-PRs:

1. Framework: gossamer, not Tauri/Dioxus. The estate is standardising on hyperpolymath/gossamer — its own resource-safe Tauri/Electron replacement (Idris2 + Zig, Ephapax linear types), which already targets mobile (Phase 5: iOS/Android). Open question Welcome to neurophone Discussions! #1 resolves to gossamer; the migration target (and the "generated Java shim under src-tauri/gen/android/" plan) should be re-expressed in gossamer's terms, coordinating with the gossamer repo on its Android path.

2. SPDX clash (open question chore(deps): update reqwest requirement from 0.11 to 0.12 #6): canonical is MPL-2.0. The repo has been reverted to SPDX-License-Identifier: MPL-2.0 uniformly (PMPL was a wrong turn). Use MPL-2.0 headers; no clash remains.

(Tracked on the neurophone side as #83, which now names gossamer.)

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