Docs site: no page covers Casework task templates, task authority, or BReg agent access profiles

## What

Casework task grants shipped in v0.31.0 and were extended in v0.32.0, but the documentation site has no page for them. Nothing under `docs/site/src/content` mentions `taskTemplates`, and `taskAuthority` appears only in the changelog. The same gap covers the BReg side: `actorKind` is described on the access-profile page only as a claim constraint, and there is no page explaining what an `actorKind: agent` profile with a `taskGrant` binding is for, what it may and may not hold, or how a status client is configured.

Today the only writing on the feature is in repository notes that are not published: `products/casework/TASK_GRANTS.md`, `products/breg/TASK_GRANTS.md` and `products/casework/DEV-SOURCES.md`. An adopter reading the site cannot discover the feature at all, and an adopter who does discover it has to read Rust to configure it.

## Evidence

- `rg taskTemplates docs/site/src/content` returns nothing.
- `rg taskAuthority docs/site/src/content` matches only `docs/site/src/content/docs/changelog.mdx`.
- `rg actorKind docs/site/src/content` matches only `docs/site/src/content/docs/configure/breg.mdx` lines 131 and 133 and `docs/site/src/content/docs/configure/evidence.mdx` line 145, all of them claim-shape statements.
- The unpublished notes: `products/casework/TASK_GRANTS.md`, `products/breg/TASK_GRANTS.md`, `products/casework/DEV-SOURCES.md`.
- Configured surface that has no page: `casework.yaml:/taskTemplates` (`crates/registry-caseworkctl/src/lib.rs` line 589) and the task authority wiring in `crates/registry-caseworkctl/src/dev/integrations.rs`.

## Proposed fix

Add a configure page for task templates and task authority (template shape, subjects, bounds, agent and client identity, resource, scopes, purpose, deadline), and an operate page for the status client and its refusals. Extend the BReg access-profile page with the `actorKind: agent` plus `taskGrant` profile: what it may hold, what the compiler refuses, and how the source issuer is trusted.

## Found while

Extracting reusable App Kit skills against Registry Stack v0.32.0.

Start with products/casework/TASK_GRANTS.md, products/breg/TASK_GRANTS.md, and products/casework/DEV-SOURCES.md, then inspect the existing pages under docs/site/src/content/docs/configure and the casework.yaml and Rust entry points named in the issue. Add configure and operate coverage for task templates, task authority, status-client refusals, and BReg agent profiles, and verify the site no longer leaves these features undocumented.

Written by the indexing model from the issue text.