good first issue: improve newcomer path in docs index

[sergeyenin]

Summary: refine docs index start path for newcomers with 3 jobs-to-be-done and first contribution pointers. Acceptance: links validated and obvious next action for contributors.

[sergeyenin]

Reorganized into the Talon 2.0 backlog. This work is now tracked in #154 (milestone M1).

See the north-star demo #107 and the milestones for the full plan (internal_docs/talon-2/). Closing here to keep the board aligned with the 2.0 roadmap — history is preserved and this can be reopened if needed.