docs: scaffold documentation information architecture (Phase 1)

Add the docs/ skeleton for the full docs implementation: getting-started,
architecture, guides, reference, and vision sections, with a nav/TOC home
page. Every page is a stub carrying its heading outline and pointers to the
source material to be migrated in Phase 2 (content).

docs/nips/, docs/spec/, and the loose design docs stay at their current
paths (55 references from code, tests, and migrations outside docs/);
reference/nips.md and reference/design-docs.md index them instead.

Root GitHub-convention files are untouched. ARCHITECTURE/NOSTR/TESTING/
RELEASING/VISION* remain in place this phase and will become pointer files
in Phase 2.

Co-authored-by: npub19zza5yyr075j4vvlg2drsh2xe0xy3dqxhfchlgtw8vryglrry3gq8q7tzk <2885da10837fa92ab19f429a385d46cbcc48b406ba717fa16e3b06447c632450@sprout-oss.stage.blox.sqprod.co>
Signed-off-by: npub19zza5yyr075j4vvlg2drsh2xe0xy3dqxhfchlgtw8vryglrry3gq8q7tzk <2885da10837fa92ab19f429a385d46cbcc48b406ba717fa16e3b06447c632450@sprout-oss.stage.blox.sqprod.co>

docs/reference/cli.md

@@ -0,0 +1,16 @@
+# CLI Reference
+
+> **Status: stub — Phase 1 (structure).** Content to be written in Phase 2.
+>
+> **Scope:** Command-by-command reference for the `buzz` CLI, derived from --help output and verified against `crates/buzz-cli` source (README has known drift).
+
+## Outline
+
+- Global flags, env vars (BUZZ_RELAY_URL, BUZZ_PRIVATE_KEY, BUZZ_AUTH_TAG), exit codes
+- Command groups: messages, channels, canvas, reactions, dms, users, workflows, feed, social, repos, upload, mem
+- Examples per group
+
+## Source material
+
+- `buzz --help` and per-group `--help` (primary)
+- `crates/buzz-cli/src/` (verify — do not trust `crates/buzz-cli/README.md`)