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/vision/README.md

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+# Vision
+
+> **Status: stub — Phase 1 (structure).** Content to be written in Phase 2.
+>
+> **Scope:** Aspirational direction — NOT current behavior. Quarantined from the rest of the docs so vision statements are never mistaken for shipped features.
+
+## Outline
+
+- The relay is the workspace (core vision)
+- Index of sub-visions: activity, agent, mesh, projects, sovereign
+
+## Source material
+
+- `VISION.md` (full migration)
+- `VISION_*.md` (5 files → sibling pages)

docs/vision/activity.md

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+# Vision: Activity
+
+> **Status: stub — Phase 1 (structure).** Content to be written in Phase 2.
+>
+> **Scope:** Aspirational — not current behavior. Full migration of root VISION_ACTIVITY.md.
+
+## Outline
+
+- Migrate VISION_ACTIVITY.md content as-is, edited only for docs-tree link consistency
+
+## Source material
+
+- `VISION_ACTIVITY.md`

docs/vision/agent.md

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+# Vision: Agent
+
+> **Status: stub — Phase 1 (structure).** Content to be written in Phase 2.
+>
+> **Scope:** Aspirational — not current behavior. Full migration of root VISION_AGENT.md.
+
+## Outline
+
+- Migrate VISION_AGENT.md content as-is, edited only for docs-tree link consistency
+
+## Source material
+
+- `VISION_AGENT.md`

docs/vision/mesh.md

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+# Vision: Mesh
+
+> **Status: stub — Phase 1 (structure).** Content to be written in Phase 2.
+>
+> **Scope:** Aspirational — not current behavior. Full migration of root VISION_MESH.md.
+
+## Outline
+
+- Migrate VISION_MESH.md content as-is, edited only for docs-tree link consistency
+
+## Source material
+
+- `VISION_MESH.md`

docs/vision/projects.md

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+# Vision: Projects
+
+> **Status: stub — Phase 1 (structure).** Content to be written in Phase 2.
+>
+> **Scope:** Aspirational — not current behavior. Full migration of root VISION_PROJECTS.md.
+
+## Outline
+
+- Migrate VISION_PROJECTS.md content as-is, edited only for docs-tree link consistency
+
+## Source material
+
+- `VISION_PROJECTS.md`

docs/vision/sovereign.md

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+# Vision: Sovereign
+
+> **Status: stub — Phase 1 (structure).** Content to be written in Phase 2.
+>
+> **Scope:** Aspirational — not current behavior. Full migration of root VISION_SOVEREIGN.md.
+
+## Outline
+
+- Migrate VISION_SOVEREIGN.md content as-is, edited only for docs-tree link consistency
+
+## Source material
+
+- `VISION_SOVEREIGN.md`