fix(gateway): serve pre-rendered directories before SPA fallback

[olamide226]

Summary

• The embedded-mode file server previously rewrote all extension-less paths to /, so only the root index.html was ever served — regardless of URL
• Frameworks that emit per-route directories with index.html (Next.js with trailingSlash, Gatsby, Hugo, etc.) were broken: users always saw the landing page
• Apply a try_files-style lookup (equivalent to nginx try_files $uri $uri/ /index.html): check whether the requested path maps to a directory containing index.html on disk before falling back to root
• Pure-SPA fallback (Vite, CRA, etc.) remains fully intact — only extension-less paths with a matching dir/index.html on disk are served directly

How it works

Request	Disk state	Before	After
/signin/	signin/index.html exists	Root index.html (wrong)	signin/index.html
/signin	signin/index.html exists	Root index.html	301 → /signin/ → signin/index.html
/dashboard	No dir on disk (pure SPA)	Root index.html	Root index.html (unchanged)
/app.js	Static asset	Served directly	Served directly (unchanged)
/missing.js	Doesn't exist	404	404 (unchanged)

Test plan

• TestFileServer_RootServesIndexHTML — root serves index.html
• TestFileServer_StaticAssetServedDirectly — files with extensions served as-is
• TestFileServer_PrerenderedDirWithTrailingSlash — /signin/ serves signin/index.html
• TestFileServer_PrerenderedDirWithoutTrailingSlash — /signin redirects to /signin/
• TestFileServer_SPAFallbackForUnknownRoute — unknown routes fall back to root
• TestFileServer_SPAFallbackForTrailingSlashNoDir — trailing slash with no dir falls back (pure SPA)
• TestFileServer_MissingStaticAsset404 — missing assets with extensions return 404
• TestFileServer_DirWithoutIndexHTMLFallsBack — dir without index.html falls back to root (no dir listing)
• Full go test ./... passes

[ecc-tools]

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[ecc-tools]

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Troubleshooting

Cause	Resolution
Large repository	Analysis may timeout on repos with extensive history
API rate limits	Wait 15 minutes before retrying
Network issues	Queue timeout is 15 minutes; retry may succeed
Permissions	Verify app has Contents: Read access

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[Copilot]

Pull request overview

This PR fixes the embedded-mode file server to support pre-rendered per-route directories (e.g., from Next.js with trailingSlash, Gatsby, Hugo) by implementing a try_files-style lookup before falling back to the SPA root index.html. Previously, all extension-less paths were unconditionally rewritten to /, breaking frameworks that emit dir/index.html for each route.

Changes:

• Added a filesystem check in createFileServer to detect directories with index.html and serve them directly, falling back to root index.html only when no matching directory exists
• Added comprehensive tests covering pre-rendered directories, SPA fallback, static assets, 404s, and directory listing prevention
• Added test fixture files (signin/index.html, style.css) to support the new tests

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
gateway/internal/server/server.go	Added try_files-style directory check before SPA fallback in the file server handler
gateway/internal/server/server_test.go	Added 8 tests covering all routing scenarios for the SPA-aware file server
gateway/testdata/static/signin/index.html	Test fixture: pre-rendered page for /signin/ route
gateway/testdata/static/style.css	Test fixture: static CSS asset

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