Tooling: Avoid duplicate doctest execution in local verification

[flyingrobots]

Problem

cargo xtask verify runs cargo test --workspace --all-features, which already executes workspace doctests, and then schedules cargo test --workspace --doc --all-features a second time. This lengthens the local edit/verify loop without adding coverage.

Acceptance criteria

• The local verification gate schedules exactly one default workspace test pass.
• Unit, integration, and documentation tests remain covered.
• The Rust 1.94 and stable CI lanes remain unchanged.
• The testing workflow topic records the executable invariant and evidence.
• cargo +1.94.0 xtask verify passes.

Scope

This issue removes measured duplicate work only. Shared compilation caching, nextest, and CI cache policy are separate follow-ups.

[coderabbitai]

🔗 Related PRs

#26 - docs: add release process topic shelf [merged]
#32 - docs: add workflow standards [merged]
#43 - Prepare v0.5.0-alpha.1 release [merged]
#108 - Freeze canonical Target IR artifacts [merged]
#110 - Prepare v0.11.0-alpha.1 release [merged]

---

📝 Issue Planner

_{Check the box below or use the @coderabbitai plan command to generate an implementation plan and prompts that you can use with your favorite coding assistant.}

• Create Plan

---

🧪 Issue enrichment is currently in open beta.

You can configure auto-planning by selecting labels in the issue_enrichment configuration.

To disable automatic issue enrichment, add the following to your .coderabbit.yaml:

issue_enrichment:
  auto_enrich:
    enabled: false

💬 Have feedback or questions? Drop into our discord!