add product and tech spec

[harryalbert]

Description

Linked Issue

• The linked issue is labeled ready-to-spec or ready-to-implement.
• Where appropriate, screenshots or a short video of the implementation are included below (especially for user-visible or UI changes).

Testing

• I have manually tested my changes locally with ./script/run

Screenshots / Videos

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• Warp Agent Mode - This PR was created via Warp's AI Agent Mode

[harryalbert]

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This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
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• add product and tech spec #13855 👈 (View in Graphite)
• Add TUI orchestration tab bar specs #13832
• add reusable TUI tab bar component #13831
• rich message component #13777
• Add local child agents to TUI #13776
• add TUI multi-session registry and focused-session root projection #13775
• add TUI orchestration permission and configuration card #13717
• add reusable TUI option selector over shared option snapshots #13716 : 1 other dependent PR (#13830 )
• add reusable TUI editor view #13817
• route TUI editor input by owning-view focus #13771
• add option snapshots and adapt GUI orchestration pickers onto them #13714
• extract orchestration edit state into a frontend-neutral module #13707
• master

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