refactor(web): keep feature component helpers private - #10226

💭 This PR is mainly removing export keywords for visibility cleanup, so I want to verify none of the removed exports are still referenced elsewhere, like checking if parseTimestampMs removed from Sidebar.logic.ts is still needed by firstValidTimestampMs or other re-exports. The more relevant flag is isPreviewAutomationHostError, previously exported as Schema.is(...), now made private — the convention wants predicates exported directly, so I need to check if it's wrapped by a function with the same signature in previewAutomationErrors.ts.

1. browse_code — In apps/web/src/components/preview/previewAutomationErrors.ts, show the full file content, especially around isPreviewAutomationHostError and how it's used (any wrapper functions with the same signature). Also list all usages of isPreviewAutomationHostError across the repo.

2. browse_code — apps/web/src/components/Sidebar.logic.ts

💭 The private constant here isn't wrapped by a same-signature function, it's just used internally in fromCause, so this isn't a violation of that convention. I'm checking whether there are other Effect-related issues to flag. The rest of the PR is purely removing export keywords, which is a visibility cleanup with no Effect service violations — the removed exports like parseTimestampMs and summarizeToolGroup aren't Effect-related and fall outside the scope of this review. Since the PR doesn't touch Effect services except previewAutomationErrors.ts and nothing else applies, I'm concluding there are no findings, so I'll set the summary and title to "All clear" with empty details for the completion call.