fix(android): A2/A3/A4 — APK build doc, dead refs, modal hit targets

A2: docs/ANDROID.md — remove stale "permanent fix to come" note;
    clarify --lib is the canonical command; root-cause the upstream
    cargo-apk bug. SESSION_HANDOFF.md closes the open item.

A3: Remove dead CARD_PLAN.md references from four source module
    doc comments (theme/importer.rs, theme/plugin.rs, assets/mod.rs,
    assets/svg_loader.rs). Also fix stale "future picker UI" language
    in plugin.rs (picker shipped in Phase 7).

A4: ui_modal.rs spawn_modal_button — add min_height: Val::Px(48.0)
    so every modal action button meets Material's 48 dp touch target
    minimum. Modal button height was 42 px (2×SPACE_3 + TYPE_BODY_LG);
    now clamped to 48 px minimum. Cards at 40 dp on 360 dp phones are
    layout-constrained (7 columns) and cannot be widened.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

SESSION_HANDOFF.md

@@ -72,8 +72,8 @@ Also shipped (pre-Phase 8 but post-v0.22.0, already in CHANGELOG):
   hook confirmed `ClipboardManager.setPrimaryClip()` succeeds on Android 14.
   Hook reverted. Production path requires Interaction::Pressed + non-null `share_url`.
   Note: `adb shell input tap` doesn't deliver touch events on headless AVD (documented).
-- **`cargo apk build --lib` noisy stderr** — post-sign panic doesn't affect the
-  APK but pollutes CI output. Document `--lib` as canonical or upstream a fix.
+- [x] **`cargo apk build --lib` noisy stderr** — upstream cargo-apk bug; `--lib`
+  is the canonical command (CLAUDE.md §15.1, docs/ANDROID.md). No in-repo fix possible.
 
 ### 5. Feature completeness
 - [x] **Theme importer UI.** Done (`613bbf8`): "Scan for new themes" button in