Restructure AGENTS.md into scoped guides

Trim AGENTS.md to whole-repo, every-session facts (154 -> 110 lines) and move
subsystem guidance into docs/guides/*.md, each with paths: frontmatter and a
one-line index entry in AGENTS.md. Symlink each guide from .claude/rules/ so
Claude Code lazy-loads it by matching path; track those symlinks via a
.gitignore exception (.claude/settings.local.json stays ignored).

docs/guides/website-copy.md

@@ -0,0 +1,28 @@
+---
+paths:
+  - "keysat-xyz-landing/**"
+  - "keysat-docs/**"
+  - "keysat-registry-landing/**"
+---
+
+# Website & docs copy rules
+
+Applies to the public sites: `keysat.xyz` (keysat-xyz-landing), `docs.keysat.xyz`
+(keysat-docs, incl. shared `docs.js`), `registry.keysat.xyz` (keysat-registry-landing).
+
+## No em-dashes in user-facing copy
+
+No em-dashes in copy on the website or docs. Exceptions: decorative ornaments and
+verbatim third-party UI labels (e.g. BTCPay's "Network — mDNS"). Comments and
+docstrings inside source code are fine to keep em-dashes.
+
+## Don't rewrite copy outside scope
+
+Never rewrite user-facing copy or labels outside the explicit scope of a request.
+
+## Pricing/tier copy is a snapshot only
+
+Tier/pricing copy on the docs site is a snapshot, not a source of truth. The
+canonical sources are `keysat.xyz#tiers` (live tier cards rendered from the master
+Keysat) and `GET licensing.keysat.xyz/v1/products/keysat/policies`. When they
+disagree, the live endpoints win.