refactor(mobile): finalize portability and activity semantics

[richardsolomou]

Problem

Desktop and mobile still interpret inbox activity differently, while mobile duplicates canonical MCP, skill, task-creation, permission, plan, and session-attachment contracts. The shared contracts also need to run against Expo's React Native renderer and native fetch implementation without host-specific runtime failures.

Changes

Move shared activity and session presentation rules into core, and use API-client/core contracts directly from mobile. Keep the native host responsible for rendering and platform integration. Align the monorepo with React Native 0.81's React 19.1 renderer, and normalize standards-based URL inputs at the Expo fetch adapter boundary.

How did you test this?

• Full monorepo typecheck (24 tasks)
• Full mobile suite (327 tests)
• Biome on the mobile package
• Signed iOS simulator build on Xcode 26.6
• Dev PHX authentication against project 2, including live task-list and task-stream loading

Automatic notifications

• Publish to changelog?
• Alert Sales and Marketing teams?

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Created with PostHog Code

[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit e917fbd.}