Build the guided episode setup intake [#1326]

[glorydavid03023]

Summary

Builds the guided episode setup intake — the first usable step where a creator starts a new episode and turns raw synced recordings plus speaker context into an organized episode the rest of the workflow can build on.

From the preview app a reviewer can:

• Start a new episode and choose either a Riverside recording-link path or a multi-file upload path (a radio group).
• See each added source represented as a speaker track.
• Assign every speaker a role (Host / Guest 1 / Guest 2), with missing-name, unassigned, and duplicate-role gating.
• Add optional social links per speaker.
• Continue only when the setup is complete. The chosen source type, roles, names, and links are then carried into the next step (episode readiness), which surfaces the carried setup.

What's included

• prototype/episode-setup-intake.html — the new intake screen, wired as the first ingest step across the ingest-nav flow, the connected ingest path, the preview app (app.html), the preview shell ingest list, and the root catalog.
• preview/episode-setup-handoff.js — a small shared save/load/summary helper that carries only a genuinely complete setup (every speaker named and assigned a unique role), mirroring the existing layout-handoff.js.
• prototype/episode-readiness.html — reads the handoff and surfaces the carried source type and speakers on the next step (sessionStorage + query string, so it works both standalone and embedded in the app).

Verification

• node scripts/run-tests.mjs prototype and node scripts/run-tests.mjs preview both pass (the repo''s .builderloops/verify.json gate).
• Focused new coverage: preview/episode-setup-handoff.test.js (gate, normalization, query round-trip, storage, summary), prototype/episode-setup-intake.test.js (source paths, gated continue, role assignment, duplicate roles, handoff), and prototype/episode-readiness-setup-handoff.test.js (carried setup renders on the next step).
• Static, self-contained prototypes with no build step or dependencies; inline scripts parse; no innerHTML.

Preview notes

• Open /preview/, then the Episode ingest setup path (or /preview/app.html) — it now starts at Start a new episode. Confirm Host / Guest 1, then Continue unlocks into episode readiness with the setup summary carried forward. Adding an empty speaker or a duplicate role re-gates Continue.

Closes #1326