fix(validation): typecheck renderer in CI

[JustYannicc]

What changed

• Added a dedicated typecheck:renderer script that runs tsc -p tsconfig.renderer.json --noEmit --pretty false.
• Added a Project Checks workflow step that runs npm run typecheck:renderer before the renderer Vite build.

Why

• npm run build:renderer only runs vite build, so CI did not explicitly fail on renderer semantic TypeScript errors.

Compatibility impact

• No runtime behavior changes. This only adds validation coverage.

How tested

• npm_config_platform=linux /opt/homebrew/opt/node@22/bin/npm ci --ignore-scripts
• /opt/homebrew/opt/node@22/bin/npm run typecheck:renderer
• git diff --check
• Codex LSP diagnostics on src/renderer: 50 .tsx files scanned, 0 errors.
• GitHub Project Checks: pass, 2m18s, run 28703909169.

Performance evidence

• Original before-change baseline: renderer no-emit 4.87s real; main no-emit 1.81s real.
• After updating onto repaired base: renderer no-emit 4.96s real; main no-emit 1.69s real; renderer build 6.06s real; package script pnpm run typecheck:renderer 9.30s real.
• Final corrected-history renderer no-emit spot check: 4.24s real.

Stack validation

• Updated branch onto repaired codex/fix-validation-esbuild-platform-install head 15ee435fa6d548dae7cfbcaf6ccf24150566ae5d.
• Branch: codex/fix-renderer-typecheck-validation.
• Commit: b63e4d4.
• Branch diff against repaired base remains only the renderer typecheck validation patch: 2 files changed, 4 insertions.
• No pnpm-lock.yaml or generated metadata included.

Replaces

• N/A

[JustYannicc]

Superseded by the consolidated validation PR: #578