[kinqsradio]

See CONTRIBUTING before starting engineering work.

Change

The Markdown source pane in web/src/screens/library/page/Source.tsx used Array.findLast, which is not in the web package's ES2022 lib. With a web-only install, tsc --noEmit fails on the call, so the web package's stock build fails.

Replace it with a backward scan over the existing blocks, keeping the existing blocks[0] fallback and selecting the same line range. No tsconfig, lib, dependency or compiler-config change is included.

The failing command was the web package build, npm run build -w web (which runs tsc --noEmit && vite build). The repository root npm run build does not include the web workspace.

Checks and limits

Run from the fix/web-es2022-findlast worktree at 5a332e21:

• npm run typecheck -w web - pass.
• npm run build -w web - pass; tsc --noEmit and the Vite bundle complete.
• npx --yes prettier --check web/src/screens/library/page/Source.tsx - pass.
• git diff --check - pass.
• rg findLast web/src - no matches.
• A standalone comparison of the old and new selection - matched for lines before the first block, between blocks, on every boundary and after the last block.

Limits:

• No browser-rendered check; this is a mechanical range lookup in the scroll handler.
• No unit test added. The web package has no test script, and this change was not requested with tests.
• A web-only install was the configuration that exposed the original type error. A full workspace install can mask it through transitive esnext declarations; the committed code no longer relies on those declarations.

Workspace

• Used the outer Orbyn Engineering workspace with this target nested under repo/, and read the relevant project guides.

This contributor confirmation is not an automated claim that a host loaded policies.

Agent disclosure

• Tools: Freebuff Desktop coding agent, terminal, git, gh, npm, npx (Prettier), TypeScript and Vite.
• Models: host-selected model; the exact identifier was not exposed to the session and was not guessed. No model override was requested.
• Effort: host default; the exact setting was not separately exposed.
• Human role: requested this fix and the pull request; no human code edits.
• External sources: none. The change is original and copies no external code.