Default team chat sidebar to Tasks

[ZeroPoint95]

Changed

• In Chats, an active team overlay now opens the right sidebar on Tasks, including the manager conversation. Previously, manager conversations defaulted to Traffic.
• Tasks and Traffic remain selectable by clicking their header words or using the sidebar keyboard controls. The session remembers explicit selections independently for manager and member conversations, including when an overlay is cleared and reopened.
• Updated the built-in manuals to describe the new default.

Validation

• Focused regression coverage checks the initial Tasks view, switching both directions with mouse and keyboard, remembered selections, and unchanged sidebar geometry.
• Local make build and make pr-ready passed, including the complete touched internal/tui3 suite.
• Independent review requested no changes. Native and Windows builds, vet, laws, packed-manual tests, and an additional race-enabled probe of all four manager/member view combinations passed.
• The complete touched-package race run reported eleven failures; all eleven reproduced on unchanged dev at 8761488a2.
• GitHub CI is green at ec2b69adf.
• Live-provider TUI e2e and staging/full-tree checks were not run.

Keep this PR as a draft for manual evaluation, including after independent review.