docs: streamline & consolidate the tree (phase 6)

Problem: after the wiki-hq reorg, agent-instruction and human-doc domains
were still scattered across the repo root, with three now-redundant stub
files cluttering it. The organizing principle wasn't visible in the layout.

Change — enforce three clear buckets:
- .agents/  = how agents operate: OIKOS.md, HERMES.md (moved from root),
  shared/ conventions, domains/ schemas, skills/, and operations/ (operator
  cheatsheet + enrollment + hermes-agent, moved from root).
- knowledge/ = what exists + evidence: wiki/, GLOSSARY.md, and sources/ now
  including investigations/ (incident records are evidence/sources).
- root = substrate + two entry points (AGENTS.md, README.md), plus plans/
  as its own design-intent domain.

Moves:
- investigations/ -> knowledge/sources/investigations/ (incl. archive/, index).
- operations/ -> .agents/operations/.
- HERMES.md -> .agents/HERMES.md.
- Deleted unreferenced root stubs CAVEMAN.md, CONTRIBUTING.md, and OIKOS.md
  (its 7 remaining linkers repointed to .agents/OIKOS.md).

Consumers updated:
- inventory.yaml doc_page (agent-enrollment) + regenerated hosts/*.yaml + cards.
- tools/setup-hermes-soul.sh and bootstrap.sh (x2) -> .agents/HERMES.md.
- bin/homelab help string -> .agents/operations/hermes-agent.md.
- knowledge/operations schemas, llm-wiki, page-templates, incident-investigation
  skill, AGENTS.md/README nav -> new investigations/operations paths.
- All markdown links rewritten via the path-resolving mapper.

Left in place (substrate/executable/separate-domain): hosts/, ledger/, tools/,
plans/, oikos/, mcp/, secrets/, bin/, inventory.yaml.

Verification: docs-lint at baseline (2 intentional cross-repo refs, no new
breakage); gen-topology.py --check exit 0; build_host_files.py idempotent; all
doc_page targets resolve; Hermes provisioning scripts point at the new path.

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

knowledge/wiki/hosts/strong.md

@@ -50,13 +50,13 @@ Proxmox VE on 2026-07-01. No LXCs/VMs deployed on it yet.
   `bootstrap.sh --no-secrets` (reused the operator's existing Gitea PAT for
   the initial clone). `/opt/homelab-context`, the `homelab` CLI, and the
   5-min sync timer are live; `homelab whoami` resolves correctly. See
-  [agent-enrollment.md](../../../operations/agent-enrollment.md).
+  [agent-enrollment.md](../../../.agents/operations/agent-enrollment.md).
 - **Age key / secrets:** issued the same day over plain LAN (no Netbird
   needed — see the `--no-mesh` bootstrap.sh fix below). Key lives at
   `/etc/age/key.txt`; pubkey `age1rtwvdct6avjkr3cyxv3vue3vqx4d524fjfr3vk7xrnvyrylnry5sm54sn4`
   recorded in `inventory.yaml`. Not yet a recipient on any actual secret
   (`hello.yaml`, `gitea-pat.yaml`, etc.) — that's a separate grant, see
-  ["Granting a secret to a new client"](../../../operations/agent-enrollment.md#granting-a-secret-to-a-new-client).
+  ["Granting a secret to a new client"](../../../.agents/operations/agent-enrollment.md#granting-a-secret-to-a-new-client).
 
 ## Cluster membership
 
@@ -79,7 +79,7 @@ needed going forward.
 - [Library SSD migration plan](../../../.hermes/plans/2026-06-03_110000-library-ssd-migration-to-ludo-mini.md) — the larger project this is Phase 1 of (filename kept as-is, historical)
 - [Network](../infrastructure/network.md)
 - [SSH access](../infrastructure/ssh-access.md)
-- [Agent enrollment](../../../operations/agent-enrollment.md)
+- [Agent enrollment](../../../.agents/operations/agent-enrollment.md)
 
 ## Changelog