feat(#1213): Capability State Writer — write-side inverse of the resolver (#1225)

* feat(#1213): Capability State Writer — write-side inverse of the resolver

Adds src/capability-writer.cts (setCapabilityState + cmdCapabilitySet) and the
`gsd-tools capability set` subcommand: the write-side inverse of the capability
resolver (ADR-1213). One desired capability state projects onto the substrates —
`enabled` drives the runtime surface (canonical on/off), `gates` drive federated
config keys (hook granularity), install profile is a read-only floor — then
re-resolves and reports divergence (assert-and-report), so "off means off" holds
as a write-time invariant. Adds batched setConfigValues; routes gsd:settings
capability hook-gates through the writer. Docs: CLI-TOOLS reference, how-to,
ADR-1213, CONTEXT.md term.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* chore(#1213): add changeset for Capability State Writer (#1225)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

docs/README.md

@@ -32,6 +32,7 @@ Language versions: [English](README.md) · [Português (pt-BR)](pt-BR/README.md)
 - [Spike and sketch](how-to/spike-and-sketch.md) — use `/gsd-spike` and `/gsd-sketch` for exploratory work before committing to a plan
 - [Design a UI phase](how-to/design-a-ui-phase.md) — use the UI phase loop for frontend and visual work
 - [Develop a Capability for GSD 1.5+](how-to/develop-a-capability.md) — add feature Capabilities, hook fragments, and registry entries
+- [Turn a capability off (and keep it off)](how-to/turn-a-capability-off.md) — disable a capability via the surface, or gate individual hooks off without removing the capability
 - [Drive GSD from a tracker issue](how-to/drive-gsd-from-a-tracker-issue.md) — start a phase from a GitHub, Linear, or Jira issue
 - [Migrate from GSD 2](how-to/migrate-from-gsd-2.md) — upgrade an existing GSD 2 project to GSD Core
 - [Update GSD](how-to/update-gsd.md) — re-run the installer to pick up the latest release