Feat v0.7.11 query & HTTP ergonomics

Add four new Starlark sandbox builtins to reduce extension friction
around SQL decomposition and synchronous HTTP fan-out:

- db.count(table, filters) — integer row count
- db.aggregate(table, column, op, filters) — single-value aggregation
- db.query_batch(queries) — up to 10 query specs in one call
- http.batch(requests) — concurrent dispatch of up to 10 HTTP requests

Extract buildSelectQuery helper from dbQuery for reuse by query_batch.
21 new tests (14 db, 7 http). No new permissions or schema changes.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -2,6 +2,25 @@
 
 All notable changes to Armature are documented here.
 
+## v0.7.11 — Query & HTTP Ergonomics
+
+Four new Starlark sandbox builtins. No new permissions, no schema changes.
+
+**db module (permission: `db.read`)**
+
+- `db.count(table, filters={})` — returns integer count of matching rows.
+- `db.aggregate(table, column, op, filters={})` — single-value aggregation. `op` ∈ {count, sum, avg, min, max}. Returns int, float, or None.
+- `db.query_batch(queries)` — execute up to 10 query specs in a single call. Each spec supports the same parameters as `db.query`.
+
+**http module (permission: `api.http`)**
+
+- `http.batch(requests)` — concurrent HTTP dispatch of up to 10 requests. Individual failures return error response dicts (`status: 0`) rather than aborting the batch.
+
+**Internal**
+
+- Extracted `buildSelectQuery` helper from `dbQuery` for reuse by `db.query_batch`.
+- 21 new tests (14 db, 7 http).
+
 ## v0.7.10 — Workflow Handoff + Assignment UI
 
 Closes the three UX gaps found during v0.7.9: public→team handoff,