fix(android): hide the Databricks workspace nav chrome in the WebView shell

[fanzeyi]

Related issue

Closes #

Summary

• A workspace-hosted Omnigent is mounted as a Databricks workspace page, so
  the workspace wraps the SPA in its top-nav shell (the dark bar with the
  workspace switcher). In the Android shell that bar was still painted: it
  wastes vertical space and, worse, lets a user navigate into another workspace
  app with no way back into Omnigent.
• The electron and iOS shells already hide it; port the same fix to Android.
  New WorkspaceChromeScript holds the CSS plus the install-once JS, and
  OmnigentWebViewClient.onPageFinished evaluates it on every finished
  pinned-origin load.
• Keyed on the pinned origin, never on the URL path: the workspace serves the
  SPA on more than one mount (/ml/omnigents, /omnigent) and an auth
  redirect can land on neither, so a path guard leaves the chrome visible. The
  rule targets Omnigent's own .omnigent-app root rather than the
  monolith-owned nav markup, so it can't silently break when Databricks
  reshuffles its chrome, and is a no-op on standalone builds.

Test Plan

• cd web/android && ./gradlew :app:testDebugUnitTest --tests '*WorkspaceChromeScriptTest' --tests '*OmnigentWebViewClientTest' — 22 tests, all green.
• New WorkspaceChromeScriptTest covers the CSS contract, the install-once
  guard, and that the CSS is embedded as an escaped JS string literal.
• OmnigentWebViewClientTest now asserts injection order (chrome CSS before
  the facade, whose callback declares the page ready), injection without the
  facade fallback, that injection is not gated on the UI mount path, and that
  an off-origin load injects nothing.

Demo

Type of change

• Bug fix
• Feature
• UI / frontend change
• Refactor / chore
• Docs
• Test / CI
• Breaking change

Test coverage

• Unit tests added / updated
• Integration tests added / updated
• E2E tests added / updated
• Manual verification completed
• Existing tests cover this change
• Not applicable

Coverage notes

Unit tests cover the script contents and the injection points in the WebView
client. The visual result is the same CSS the electron and iOS shells already
apply.

Changelog

The Android app no longer shows the Databricks workspace navigation bar around
Omnigent when connecting to a workspace-hosted server.

Signed-off-by: Zeyi (Rice) Fan zeyi.f@databricks.com