Add Prebid.js NPM integration with per-module JS builds

[aram356]

Summary

Replaces the old Prebid extension shim (ext/prebidjs.ts) with a full NPM-bundled Prebid.js integration and introduces per-module JS builds with runtime concatenation.

Prebid.js NPM Integration

• Bundles prebid.js ^10.18.0 directly (replaces the old shim that expected a publisher-provided pbjs global)
• Registers a custom trustedServer bid adapter that routes all bid requests through the /auction orchestrator endpoint
• Shims pbjs.requestBids() to inject the trustedServer bidder into every ad unit automatically
• Server-side config (account_id, timeout, debug, bidders) injected via window.__tsjs_prebid from trusted-server.toml
• Server expands the trustedServer bidder placeholder to real PBS bidders (e.g., mocktioneer) before forwarding to Prebid Server

Per-Module JS Build Pipeline

• Each integration is now built as a separate IIFE at compile time (tsjs-core.js, tsjs-prebid.js, tsjs-creative.js, etc.)
• New build-all.mjs script replaces the single Vite build, building core + each integration in parallel
• build.rs auto-discovers dist/tsjs-*.js files and generates tsjs_modules.rs with include_str!() for each
• At runtime, the server concatenates only enabled modules based on IntegrationRegistry config
• Module selection is now a config change — no JS rebuild needed
• URL stays /static/tsjs=tsjs-unified.min.js?v=<hash> for backward compatibility

Auction Flow (Browser → Server → PBS)

1. Browser: Prebid.js trustedServer adapter → POST /auction (AdRequest format)
2. Server: handle_auction → AuctionOrchestrator → PrebidAuctionProvider
3. Server: Converts AdRequest to OpenRTB, expands trustedServer → configured bidders
4. Server: POST {server_url}/openrtb2/auction → Prebid Server
5. Server: Parses OpenRTB response, rewrites creatives → returns to browser

Core JS Cleanup

• Removed dead exports: getAllCodes, isArray, renderCreativeIntoSlot, writeHtmlToIframe
• Moved types to proper modules: Config → config.ts, RequestAdsCallback/RequestAdsOptions → request.ts
• Removed unused RequestMode enum
• types.ts now only contains the public API contract (TsjsApi, AdUnit, Size)

Key Files Changed

Area	Files
Prebid adapter	crates/js/lib/src/integrations/prebid/index.ts (new)
Shared auction	crates/js/lib/src/core/auction.ts (new), request.ts
Build pipeline	build-all.mjs (new), build.rs, bundle.rs, vite.config.ts
Module registry	registry.rs (js_module_ids()), tsjs.rs, html_processor.rs, publisher.rs
Prebid server-side	prebid.rs (head injector, bidder expansion, logging)
Deleted	ext/prebidjs.ts, ext/index.ts, ext/types.ts

Bundle Size Impact

Publishers without Prebid: ~15KB (core only, down from ~218KB unified)
Publishers with Prebid: ~215KB (core + prebid module, similar to before)

Test plan

• npx vitest run — 148 JS tests pass (16 test files)
• cargo test --workspace — 353 Rust tests pass
• npm run build — 8 module files produced in dist/
• Playwright diagnostic confirms /auction request fires on live page
• Verify Prebid Server returns 200 with valid stored request / account config
• Verify creative rendering in iframe after successful auction
• Test with Prebid disabled — verify bundle excludes tsjs-prebid.js

Closes #250
Related to #179

[ChristianPavilonis]

Looks good, currently isn't working for me, I get bids back from trusted server but nothing renders and I get this error:

ERROR: Trying to make a request for bidder that does not exist: mocktioneer

I'm not sure if there's more setup I need or if this isn't 100% done yet.