AGT-02: Add tool registry, policy evaluator, and bounded inbox-triage template

[Chris0Jeky]

Context

Tracked by: #335

Once run entities exist, Taskdeck still needs a coherent runtime abstraction for what agents may do and what they must not do.
This issue captures the blueprint's tool-registry and policy-evaluator layer together with the first bounded assistant template.

Sources:

• docs/InReview/MVP_EXPANSION/EXPANDED/taskdeck_expansion_blueprint_2026-03-06/04_BACKEND_AND_DOMAIN_EXPANSION_PLAN.md
• docs/InReview/MVP_EXPANSION/EXPANDED/taskdeck_expansion_blueprint_2026-03-06/05_AGENT_WORKSPACE_ARCHITECTURE.md
• docs/InReview/MVP_EXPANSION/EXPANDED/taskdeck_expansion_blueprint_2026-03-06/08_SEEDED_ISSUES_READY_TO_CREATE.md
• docs/InReview/MVP_EXPANSION/EXPANDED/taskdeck_expansion_blueprint_2026-03-06/snippets/backend/AgentRunService.cs

Depends on

• AGT-01: Add agent profile/run/event foundation and manual-run API #336

Coordinates with

• UX-17: Improve proposal readability and board-centered action flow #326 for proposal-summary and board-context review overlap

Scope

• Add ITaskdeckTool and ITaskdeckToolRegistry abstractions for bounded runtime actions.
• Add tool metadata including key, description, scope, and risk classification.
• Add an IAgentPolicyEvaluator or equivalent policy service covering allowlists, review thresholds, and explicit scope controls.
• Keep low-risk auto-apply off by default.
• Add the first narrow template assistant: inbox triage assistant.

Acceptance Criteria

• Runtime actions route through a testable registry instead of ad-hoc service wiring.
• Policy evaluation can answer both is this tool allowed? and must this remain review-first?.
• Policy decisions are traceable in run output/events.
• A bounded inbox-triage template can gather context and create proposals without broad autonomy claims.
• Tests cover registry resolution, policy decisions, and bounded template behavior.

Verification

• dotnet test backend/tests/Taskdeck.Application.Tests/Taskdeck.Application.Tests.csproj -c Release --filter "FullyQualifiedName~Tool|FullyQualifiedName~Policy|FullyQualifiedName~Agent"
• optional bounded scenario acceptance run once substrate exists

Suggested branch

• agt/tool-registry-policy-template

[Chris0Jeky]

Closing as delivered — all code, tests, and PR are on main.

PR #502 implemented the full AGT-02 scope:

• ITaskdeckTool / ITaskdeckToolRegistry domain interfaces with ToolScope / ToolRiskLevel enums
• PolicyDecision immutable value object (AllowWithReview, Deny, AllowDirect factory methods)
• AgentPolicyEvaluator — allowlist + risk-level gating, review-first default for ALL risk levels
• InboxTriageAssistant bounded template — gathers inbox items, creates proposals only, zero direct board mutations
• Singleton registry with scoped evaluation wired in DI

42 tests cover registry resolution, policy decisions (all branches), and bounded template behavior. All 413 tests pass green.