Greptile Summary

This PR narrows internal Discord and Matrix import paths away from broad barrel files (discord.js, matrix.js) toward seam-specific facade modules (discord-runtime-surface.js, discord-thread-bindings.js, discord-surface.js, discord-session-key.js, matrix-surface.js, matrix-runtime-surface.js, matrix-thread-bindings.js). It also refactors the types-channel.ts type map to use named module-level type aliases instead of repetitive inline typeof import(...) expressions. No behavioral changes are introduced.

• All narrowed import targets were verified to export the required symbols — no missing exports detected.
• runtime-discord-ops.runtime.ts correctly consolidates two previously duplicated import blocks (both pulling from the same discord.js barrel) into a single block pointing to discord-runtime-surface.js.
• registry.ts correctly splits the former matrix.js import into matrix-runtime-surface.js (runtime-activation path for setMatrixRuntime) and matrix-surface.js (bundled-public path for createMatrixThreadBindingManager / resetMatrixThreadBindingsForTests), which reflects the different loader semantics each surface uses.
• The type alias pattern introduced in types-channel.ts (DiscordRuntimeSurface, DiscordThreadBindings, MatrixThreadBindings) improves readability and will reduce churn when the underlying surface modules evolve.

Confidence Score: 5/5

• Safe to merge — purely a mechanical import-path narrowing with no logic changes and all target exports verified.
• Every symbol imported from the new narrow facades was confirmed to be exported by those modules. The consolidation in runtime-discord-ops.runtime.ts and the type-alias cleanup in types-channel.ts are correct and non-breaking. No behavioral code was altered.
• No files require special attention.

_{Reviews (1): Last reviewed commit: "Merge branch 'main' into fix/browser-sea..." | Re-trigger Greptile}