Make empty/loading/error copy lawyer-friendly

From the PR description

Summary

Sweeps the frontend for generic empty, loading, and error strings and replaces them with action-oriented, lawyer-friendly copy that names the next step. Frontend-only; no backend changes.

Empty states

Loading states

• DocumentCard.tsx: "Processing..." → "Reading the document..."
• AddDocumentsModal.tsx, AddProjectDocsModal.tsx, AddNewTRModal.tsx upload buttons: "Uploading..." → "Uploading your document..."
• login/page.tsx: "Logging in..." → "Logging in..."
• signup/page.tsx: "Creating account..." → "Creating your account..."; "Redirecting you to the home page..." → "Taking you to Gary..."

Error states

• error.tsx: now accepts reset from Next, shows a Try Again primary CTA plus a Return Home secondary CTA. Body copy: "Gary hit an unexpected problem. Try again, or return home."
• global-error.tsx: Back button → Try Again wired to reset(). Body copy mirrors the above.
• not-found.tsx: CTA renamed Go home → Return Home, body softened.
• DocumentCard.tsx: "Upload failed" → "Upload failed - try again"
• TRChatPanel.tsx streaming error: "An error occurred. Please try again." → "Something went wrong. Try asking again."
• NewProjectModal.tsx: "Failed to create project" → "Could not create the project. Try again."
• NewWorkflowModal.tsx: "Failed to update/create workflow" → "Could not save/create the workflow. Try again."
• useFetchSingleDoc.ts: "Failed to load document." → "Could not load the document. Try again."
• login/page.tsx: "An error occurred during login" → "Could not sign in. Check your email and password and try again."
• signup/page.tsx: "An error occurred during signup" → "Could not create your account. Try again."
• account/page.tsx alerts: "Failed to delete account / update display name / update organisation" → "Could not delete your account / save your display name / save your organisation. Try again."
• account/models/page.tsx: Failed to save ${label}. → Could not save your ${label}. Try again.

console.error lines and thrown internal errors (e.g. throw new Error("HTTP ..."), hook misuse messages) are unchanged - the developer view stays technical.

Technical surfaces remaining (reported, not changed)

Per the brief - "If not easy, leave them and report where they are":

• /account/models - the page literally exposes Anthropic / Google API key inputs. Title "API Keys" and labels "Anthropic (Claude) API Key" / "Google (Gemini) API Key" remain. This is the existing settings/advanced area; renaming "API key" away would be misleading and would require renaming the sidebar/account tab too.
• ApiKeyMissingModal.tsx - title "API key required" and body "You haven't added a {provider} API key yet..." remain. The modal redirects to /account/models. Same reasoning.
• ModelToggle still surfaces model names ("Claude Opus 4.7", "Gemini 3.1 Pro") inside ChatView and in /account/models. PR #6 already hid it from the home empty state.
• AppSidebar nav still labels "Tabular Review" and "Workflows" - feature names; left as-is to avoid renaming routes.
• text-search-widget.tsx "No results" - inline text-find-in-document message; left as-is, feels right in that micro-context.
• EmailPillInput.tsx "Could not verify email. Try again." - already lawyer-friendly.
• Reasoning-block phrases ("Thinking...", "Pondering...", "Analyzing...", "Reasoning...") are kept; they're already approachable.

Files changed

Frontend only - 25 files, +93/-79. Zero backend files touched (git diff main..HEAD -- backend/ is empty). License unchanged.

Build / lint / tests

• npm run lint - 107 problems vs. 108 on main (one fewer; baseline issues all predate this PR; no new errors or warnings introduced in the changed files).
• npx tsc --noEmit - clean.
• npm run build - same fonts.googleapis.com sandbox network failure on main and on this branch; not a code issue. Cloudflare Workers Builds will run a real build on the PR.
• No test scripts in either package.json.

Test plan

• Workers Build for this PR succeeds.
• Sign out and visit /login with bad credentials - friendlier error appears.
• Brand new account with no projects - /projects shows "No projects yet" with the new description and "+ Create Project" CTA.
• Empty /tabular-reviews shows "No reviews yet" with the lawyer description and "+ Create Review".
• On /assistant, sidebar history shows "No chats yet. Ask Gary a question to start one."
• Upload a small PDF - DocumentCard shows "Reading the document..." while it's processing.
• Open a project with no documents - drop zone says "Drop a PDF or Word document here, or click to upload."
• Visit a non-existent path like /foo - not-found page shows "Return Home".
• Trigger a render error - error boundary shows the new copy with Try Again + Return Home.

https://claude.ai/code/session_019pRkhcGDRKQWHjzAnV5yCL

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