Implement structured Android entry viewer (#99)

docs/android/entry-viewer.md

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+# Android structured entry viewer (#99)
+
+The viewer renders Rust-provided sections and fields without parsing or serializing
+entries in Compose. Passwords, PINs, OTP URIs and other sensitive fields start masked.
+Reveal, copy and edit use the field ID together with the exact document revision.
+An external replacement rejects the old field IDs and locks the authentication
+lease. Editing saves through Rust's recoverable encryption and automatic Git commit
+workflow, then refreshes the checked navigation and document revisions.
+
+Rust supplies TOTP codes, account labels and remaining seconds. The presentation
+refresh does not renew the lease. Expiry, backgrounding and manual lock remove
+sections, codes, editor inputs and mutation dialogs. Decrypted values never enter
+saved state; secret-bearing facade objects redact their string representation.
+
+The Material top bar offers an editable-field picker and Move, Copy and Delete
+plans. Rust supplies destinations, overwrite requirements and checked mutation
+revisions. Confirmation is explicit. Compact and adaptive list/detail panes share
+the same viewer; wrapped values, multiline notes and repeated fields remain intact.
+Headings, labelled actions and keyboard submission expose the same typed operations.
+
+Only fields marked selectable by Rust permit text selection. Selection-copy and
+explicit Copy both request the complete stored field from Rust, preserving its
+clipboard timeout. The editor explains that copying uses the saved value; saving
+first makes edits available to copy. Android marks clips sensitive, and Rust clears
+its own clip on timeout or lock without restoring previous clipboard contents or
+erasing a newer clip. Screen capture is blocked for the activity and dialogs.
+
+## Validation
+
+Rust regressions cover revision-bound field actions, external edits, lease expiry,
+TOTP countdown boundaries and clearing clipboard behavior. Existing document
+fixtures cover dynamic, repeated, multiline, Unicode, malformed and OTP-only
+entries without replacing their original format. Native Android instrumentation
+creates an isolated GPG-encrypted store through Rust and exercises reveal, hide,
+copy, save, copy/delete mutations, stale revisions and expiry during TOTP refresh.
+Compose checks cover masking, field actions, diagnostics, dialog revocation,
+mutation confirmation, clipboard sensitivity and screen-capture protection.
+All four required Rust workspace gates and the complete Android build, lint,
+dependency/license, module-boundary and native-package gates passed. Full app,
+core and bridge instrumentation plus five cold starts passed on ARM64 API 26/4 KB,
+API 37/4 KB and API 37/strict 16 KB. Both ARM64 and ARMv7 release artifacts were
+built and audited.
+
+Computer use in Android Studio's embedded emulator checked the disposable viewer,
+masked PIN editor, repeated fields, Unicode and contextual selection at 200% font
+size. Native contextual Copy was observed dispatching the Username's field ID.
+Manual TalkBack speech was not checked; labelled accessibility actions are covered
+by instrumentation. ARMv7 is built and packaged but has no available emulator
+image. Physical-device testing is outside this milestone's scope.