fix(examples): add missing workspace fields to governance interceptor

[pavelanni]

Summary

The ListSandboxesRequest proto gained workspace and all_workspaces fields as part of the workspace feature, but the governance interceptor example was not updated, causing a compilation failure:

error[E0063]: missing fields `all_workspaces` and `workspace` in initializer of
              `openshell_core::proto::ListSandboxesRequest`

Sets all_workspaces: true so the interceptor's policy reload covers sandboxes across all workspaces.

Related Issue

None — found while running examples/governance-interceptor/smoke.sh on current main.

Changes

• Added workspace: String::new() and all_workspaces: true to the ListSandboxesRequest initializer in the policy reload loop (src/main.rs)

Testing

• cargo build --manifest-path examples/governance-interceptor/Cargo.toml compiles successfully
• ./smoke.sh starts the gateway and interceptor without build errors

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[drew]

/ok to test c7e3e18

[pavelanni]

@drew This PR got pulled from the merge queue overnight with "removed this pull request from the merge queue due to no response for status checks" — looks like a timing race with the /ok to test gate (the queue attempt happened before CI was authorized to run). All checks are now green and the PR shows as mergeable. Could you re-add it to the merge queue when you have a moment? Thanks again for the review!