Add explicit touch Clear search controls to launcher and Emoji #110

Part of #1 and #71; follows the audited test-contract correction in #109. #69 remains open: this is an explicit touch alternative, not a claim to repair system-IME keyboard handling.

The native launcher and Emoji headers currently provide editable search and keyboard/category controls, but no visible Clear search action. A touch user must erase the query manually.

Acceptance criteria:

• Add a recognizable close glyph with the accessibility label “Clear search” to each header when its query contains characters, including whitespace. Reserve its layout space when empty so typing/clearing does not shift the search field.
• Provide a nonoverlapping 48 dp target within the palette. Preserve useful editor width and existing Back/category/keyboard controls on phone, tablet and short landscape, including 200% text. Do not reduce font scale.
• One pointer tap clears the live text, selection/composition and result selection; retain the active route/category, existing editor focus and keyboard intent. Do not copy, launch a result or navigate away.
• Reject retained actions after their surface/epoch is replaced, disposed, covered by a menu/review, or loses window ownership. A current action clears the current query even if it changed before recomposition.
• Verify actual pointer clearing with ordinary system IME and explicitly controlled composition, empty-state removal, stable geometry, category preservation, and stale callback rejection. Retain relevant existing Emoji/header and keyboard regressions. Include an API26 smoke check, bounded to this explicit action.
• Publish real before/after Android screenshots with frozen build/APK identities and readable error/empty/return states where relevant. Use a common test harness for old-app negative controls. Preserve original installed data/settings and record restoration; keep failures and diagnostics distinct.
• Record local checks separately from actual exact-head hosted Android CI. Obtain two independent gpt-6.1-sol/high full-head audits, fix findings and merge only the reviewed verified head with an expected-head guard.

This does not certify physical typing, TalkBack/OEM, all typography, arbitrary extension search surfaces or whole-Store parity. #69/#71 and other documented gaps remain open.