fix: improve Mac connectivity and session handling

[MRL-00]

Summary

Fix cold-start Mac detection, bounded main-page refreshes, project-folder error handling, and session creation/navigation.

What changed

• retry Mac discovery at startup and when returning to the foreground
• bound manual refresh requests and prevent stale overlapping loads
• show folder browsing and add-project failures instead of silently ignoring them
• add a session menu for creating and switching sessions
• surface session creation failures
• bump the iOS build number to 20 for TestFlight

User impact

Macs should appear online without first visiting Manage Macs, refreshes finish, selected project folders appear or report a useful error, and users can start new sessions within an existing workspace.

Validation

• iOS Simulator Debug build passed
• git diff checks passed
• no server files changed

Known warnings or follow-ups

The existing UIScreen.main iOS 26 deprecation warning remains unrelated to this change.

Summary by CodeRabbit

• New Features

  • Added a toolbar menu for creating new chat sessions and switching between existing sessions.
  • Selecting a session restores its conversation, model settings, and message updates.
  • Chat drafts are preserved when session creation fails.

• Bug Fixes

  • Improved project loading with retries, cancellation, and protection against outdated results.
  • Added clear error messages for failed project, folder, session, and server requests.
  • Improved Mac connection status and refresh behavior when returning to the app.
  • Folder confirmation is disabled while folder contents are loading.

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Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: fe534703-44eb-4bf4-870c-75b7375b0b65

📥 Commits

Reviewing files that changed from the base of the PR and between b169b74 and b752ab3.

📒 Files selected for processing (4)

• PiMobile.xcodeproj/project.pbxproj
• PiMobile/APIClient.swift
• PiMobile/Views/ChatView.swift
• PiMobile/Views/ProjectsView.swift

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📝 Walkthrough

Walkthrough

The PR updates API timeout and error handling, adds retry and stale-load protection for projects, adds chat session creation and switching flows, and increments the Debug and Release project versions.

Changes

App reliability and session management

Layer / File(s)	Summary
API timeout and error handling PiMobile/APIClient.swift	APIClient.get applies request timeouts and decodes non-200 responses as APIError.server. repos(on:) accepts an optional timeout.
Project loading and folder feedback PiMobile/Views/ProjectsView.swift	ProjectsView adds bounded retries, cancellation, stale-load suppression, scene activation refreshes, connectivity states, project error alerts, and folder-loading feedback.
Chat session creation and switching PiMobile/Views/ChatView.swift	ChatView adds session creation state, session selection, explicit creation errors, draft restoration, message refreshes, and polling resumption.
Build version update PiMobile.xcodeproj/project.pbxproj	Debug and Release configurations increase CURRENT_PROJECT_VERSION from 18 to 20.

Estimated code review effort: 3 (Moderate) | ~25 minutes

Sequence Diagram(s)

sequenceDiagram
  participant ProjectsView
  participant APIClient
  participant MacServer
  ProjectsView->>APIClient: Request repositories with timeout
  APIClient->>MacServer: Send HTTP request
  MacServer-->>APIClient: Return repositories or HTTP error
  APIClient-->>ProjectsView: Return result
  ProjectsView->>ProjectsView: Retry, cancel, or discard stale result

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Possibly related PRs

• MRL-00/pi-mobile#8: Shares the same app files and extends the Pi app functionality.
• MRL-00/pi-mobile#9: Directly relates to chat session creation and send error handling.
• MRL-00/pi-mobile#10: Relates to API error handling and chat session behavior.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/fix-connectivity-sessions

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