chore(agent): drop dev-skip-broker-signature cargo feature

[Benoît Cortier (CBenoit)]

Removes the development-only dev-skip-broker-signature cargo feature.
Skipping package broker client signature validation is already opt-in through the __debug__.skip_broker_signature_validation configuration option (off by default), the same model as skip_msi_signature_validation.
The extra compile-time gate only duplicated that control and required a dedicated CI step to run some tests.

Changes:

• Drop the feature from now-package-broker and devolutions-agent; the debug option is now honored directly (a DEBUG MODE warning is still logged when the bypass is used).
• Policy route authorization tests in now-package-broker are no longer feature-gated, so they run with the regular cargo test --workspace.
• Remove the Run policy route authorization tests CI step and build the agent for the policy tester without --features; the tester still enables the bypass through its generated agent.json.

Reviewer note: on a production build, whoever can edit agent.json can now disable broker client signature validation. The trusted-writer check on the client executable is not affected by the bypass.

Follow-up to #1981.

🤖 Generated with Claude Code

[Benoît Cortier (CBenoit)]

Implementation notes:

• signature_validation_skipped() in now-package-broker/src/auth.rs is removed; validate_connection checks the flag directly.
• The shipping_build / dev_build test modules are merged into two tests: validate_connection_validates_signature_unless_skipped (unsigned test binary fails without the bypass, passes with it) and signature_bypass_does_not_disable_trusted_writer_security.
• shared_router_exposes_policy_management_routes now only asserts the bypass-enabled statuses, since test state always sets skip_signature_validation: true.
• Verified locally: cargo +nightly fmt --all, cargo clippy -p now-package-broker -p devolutions-agent --tests -- -D warnings, and cargo test -p now-package-broker (430 passed, 2 ignored).

[Copilot]

Copilot review overview

🔵 Needs a closer look

A production security bypass needs explicit human acceptance, and the revised test does not verify signature enforcement when the bypass is off.

Review effort: Balanced
Findings: 1

Open (1)

• Test does not verify unsigned executable rejection · New

What changed in this PR

This PR removes the development-only Cargo gate for the Agent’s package-broker signature bypass. The debug configuration option now controls the bypass in all builds.

Changes:

• Remove the feature gate and its dedicated CI test step.
• Run policy route authorization tests in the regular workspace test run.
• Update signature-validation tests for the new behavior.

File	Description
devolutions-agent/​src/​service.rs	Passes the debug bypass setting to the broker.
devolutions-agent/​src/​config.rs	Removes the obsolete feature-gate documentation.
devolutions-agent/​Cargo.toml	Removes the Agent feature.
crates/​now-package-broker/​src/​server/​mod.rs	Ungates route authorization tests.
crates/​now-package-broker/​src/​auth.rs	Removes the gate and revises authentication tests.
crates/​now-package-broker/​Cargo.toml	Removes the broker feature.
.github/​workflows/​ci.yml	Builds without the feature and removes its dedicated test step.

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