feat(examples): add supervisor middleware content guard

[pimlock]

Summary

Add a runnable supervisor middleware content-guard example for the middleware shipped in #2027. The example demonstrates operator-run service registration, policy attachment, request-body inspection, and allow, deny, and redact responses.

Related Issue

Related to #1733

Changes

• Add a standalone Rust content-guard gRPC service using the supervisor middleware API
• Support configurable term matching with redact and deny modes, audit-safe findings, and a stable deny reason code
• Add an example policy using the keyed network_middlewares format and operator-owned registration name
• Add smoke.sh to build and launch the gateway, middleware, and sandbox with automatic cleanup
• Demonstrate the same payload going through a guarded httpbin.org request and an unguarded httpbingo.org request
• Document the smoke flow, openshell.supervisor.middleware registration, body limit, and timeout behavior
• Keep the example lockfile reproducible and aligned with the current workspace dependencies

Testing

• mise run pre-commit passes
• examples/supervisor-middleware-content-guard/smoke.sh --test-suite passes
• cargo test --manifest-path examples/supervisor-middleware-content-guard/Cargo.toml passes
• Unit tests cover redaction, denial and reason code, pass-through, and invalid configuration
• Smoke coverage verifies a selected request is filtered and an allowed unselected request is unchanged

Checklist

• Follows Conventional Commits
• Commits are signed off (DCO)
• Architecture docs updated (not applicable, the middleware architecture and user documentation landed in feat(supervisor-middleware): add network egress middleware #2027)

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[pimlock]

/ok to test 06c0433

[pimlock]

/ok to test e8e6456

[drew]

gator-agent

PR Review Status

Validation: This PR is project-valid because it adds a focused runnable example for the supervisor middleware roadmap tracked by #1733.
Head SHA: bf8937e60420fee61a22688495d13a2ea92f6f62

Review findings:

• Two warnings should be fixed before gator can move this PR to pipeline watch.

Docs: Example README is included; published Fern docs already cover the registration and policy fields used here, so no navigation change is required for this example-only addition.

Checks: Required branch checks, Helm Lint, Markdown, license, DCO, and Rust jobs are currently passing.

E2E: Deferred until review feedback is resolved.

Next state: gator:in-review

[drew]

gator-agent

PR Review Status

Validation: This PR is project-valid because it adds a focused runnable example for supervisor middleware work related to #1733.
Head SHA: e860e01192069af7f556e992999f8f266e4f3f1d

Thanks @pimlock, I checked your follow-up on the prior gator findings. The optional-field validation now rejects malformed mode and replacement values, and the smoke launcher now resolves the root and example Cargo target directories before launching binaries.

Review findings:

• One warning remains on redaction behavior for overlapping configured terms.

Docs: Example README is included; this is example-local UX documentation, so I do not see a Fern docs or navigation update requirement for this PR.

Checks: DCO, Markdown, License Headers, Helm Lint, and several branch-check jobs are passing; OpenShell / Branch Checks and Rust jobs are still pending on the current head.

E2E: test:e2e is not applied yet. E2E should be decided after review feedback is resolved.

Next state: gator:in-review

[drew]

gator-agent

PR Review Status

Validation: This PR is project-valid because it adds a focused runnable example for supervisor middleware work related to #1733.
Head SHA: 2f5751a706e894853ebe5bd46b2fe4f8adc1f2d6

Thanks @pimlock, I checked the latest update. The optional-field validation and target-directory handling remain resolved, and the new longest-first ordering fixes the prefix-overlap case from the prior review.

Review findings:

• One warning remains on redaction behavior for partially overlapping configured terms.

Docs: Example README is included; this is example-local UX documentation, so I do not see a Fern docs or navigation update requirement for this PR.

Checks: DCO, Markdown, License Headers, Helm Lint, Branch Checks, Rust, Python, and mise Lockfile are passing on the current head.

E2E: test:e2e is not applied yet. E2E should be decided after review feedback is resolved.

Next state: gator:in-review

[drew]

gator-agent

PR Review Status

Validation: This PR is project-valid because it adds a focused runnable example for supervisor middleware work related to #1733.
Head SHA: 9ca89d99c3ca7bb7fcecebd2f79b9584505f521f

Thanks @pimlock, I checked the README warning-alert update in this head. The docs markup change is fine, but the redaction behavior issue from the prior head is still present because the Rust code did not change.

Review findings:

• One warning remains on redaction behavior for partially overlapping configured terms.

Docs: Example README is included; this is example-local UX documentation, so I do not see a Fern docs or navigation update requirement for this PR.

Checks: CI has restarted for this head; DCO is passing, and Branch Checks, Helm Lint, Rust, Python, Markdown, License Headers, and mise Lockfile are pending.

E2E: test:e2e is not applied yet. E2E should be decided after review feedback is resolved.

Next state: gator:in-review

[drew]

gator-agent

PR Review Status

Validation: This PR is project-valid because it adds a focused runnable example for supervisor middleware work related to #1733.
Head SHA: 0623b7030ff867e775b345915039e990af2c9b23

Thanks @pimlock, I checked your latest follow-up on the overlapping redaction findings. The current implementation computes matches from the original UTF-8 body, merges overlapping ranges, rebuilds the redacted body once, and includes partial/self-overlap regression coverage.

Review findings:

• No blocking findings remain.

Docs: Example README is included; this is example-local UX documentation, so I do not see a Fern docs or docs/index.yml navigation update requirement.

Checks: Required Branch Checks, Helm Lint, DCO, Markdown, License Headers, Rust, Python, and mise Lockfile are passing on the current head.

E2E: test:e2e is required for this supervisor middleware/network-policy smoke example and is being applied for pipeline monitoring.

Next state: gator:watch-pipeline

[github-actions]

Label test:e2e applied for 0623b70. Open the existing run and click Re-run all jobs to execute with the label set. The run will execute the standard E2E suite after building the required gateway and supervisor images once. The matching required CI gate status on this PR will flip green automatically once the run finishes.

[drew]

gator-agent

Monitoring Complete

Monitoring is complete because this PR has merged.

Final status: The last gator state was gator:merge-ready; review had no blocking findings, required checks and test:e2e were complete, and maintainer approval was present before merge.

I removed the active gator:* label because there is nothing left for gator to monitor on this PR.