fix: [nomad-step-2] S2.1 — vault/policies/*.hcl + tools/vault-apply-policies.sh (#879)

Land the Vault ACL policies and an idempotent apply script. 18 policies:
service-{forgejo,woodpecker}, bot-{dev,review,gardener,architect,planner,
predictor,supervisor,vault,dev-qwen}, runner-{GITHUB,CODEBERG,CLAWHUB,
NPM,DOCKER_HUB}_TOKEN + runner-DEPLOY_KEY, and dispatcher.

tools/vault-apply-policies.sh diffs each file against the on-server
policy text before calling hvault_policy_apply, reporting created /
updated / unchanged per file. --dry-run prints planned names + SHA256
and makes no Vault calls.

vault/policies/AGENTS.md documents the naming convention (service-/
bot-/runner-/dispatcher), the KV path each policy grants, the rationale
for one-policy-per-runner-secret (AD-006 least-privilege at dispatch
time), and what lands in later S2.* issues (#880-#884).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vault/policies/service-forgejo.hcl

@@ -0,0 +1,15 @@
+# vault/policies/service-forgejo.hcl
+#
+# Read-only access to shared Forgejo secrets (admin password, OAuth client
+# config). Attached to the Forgejo Nomad job via workload identity (S2.4).
+#
+# Scope: kv/disinto/shared/forgejo/* — entries owned by the operator and
+# shared between forgejo + the chat OAuth client (issue #855 lineage).
+
+path "kv/data/disinto/shared/forgejo/*" {
+  capabilities = ["read"]
+}
+
+path "kv/metadata/disinto/shared/forgejo/*" {
+  capabilities = ["list", "read"]
+}