docs(readmes): fix stale facts in remaining crate READMEs + gotchas

- frontend/README.md: list the missing packages/swarm-ui package, fix
  the vanilla-JS claim (all packages depend on preact), and the
  deprecated hyperhive.frontend.extraFiles spelling
- hive-c0re/README.md: hive-c0re no longer provisions per-agent
  forge/matrix accounts (swarm-controller does); it wires gateway
  vhosts and reconciles forge/matrix config
- hive-metric/README.md: OTEL_EXPORTER_OTLP_HEADERS is never set by
  the harness and has no way to be set
- hive-agent-sock/README.md: fix the deprecated
  hyperhive.extraMcpServers spelling
- docs/process/gotchas.md: fix a dangling hive-ag3nt/ path, the real
  directory is hive-agent/

Also fixes pre-existing vale error-level alerts (passive voice,
Microsoft.Auto, Microsoft.Contractions) in the same files so
prose-lint-errors passes clean.

hive-c0re/README.md

@@ -2,15 +2,17 @@
 
 The unprivileged host daemon (runs as `hive-core`). Owns the sqlite
 broker, the approval/reminder/schedule queues, the generic job-DAG
-queue, container lifecycle, gateway/forge/matrix provisioning,
-per-container stats, and the axum operator dashboard. Largest crate in
-the workspace — bin-only, no separate lib.
+queue, container lifecycle, gateway vhost wiring, forge/matrix config
+reconciliation, per-container stats, and the axum operator dashboard.
+Largest crate in the workspace — bin-only, no separate lib.
 
 ## When to use it
 
 Host-level, cross-container orchestration: spawning/rebuilding/
 destroying agent containers, the approval flow, dashboard-visible
-state, provisioning per-agent forge/matrix/gateway accounts. Agent-side
+state, wiring each agent's gateway vhost and reconciling its forge
+config-repo access and matrix room membership. The accounts themselves
+are swarm-controller's (`docs/integrations/forge.md`). Agent-side
 behavior (turn loop, MCP tools) lives in `hive-agent`/`hive-agent-mcp`
 instead — this daemon only talks to agents over the socket wire types
 in `hive-sh4re`.
@@ -31,7 +33,7 @@ to track it:
   flake generation.
 - **`stores/`** — sqlite-backed stores (broker, queues, audit, power).
 - **`workers/`** — background sweeps (crash watch, scheduled prompts,
-  auto-update, knowledge sync).
+  autoupdate, knowledge sync).
 - **`agent_config/`** — per-agent registries (tool groups,
   capabilities, resource limits, topology).
 - **`stats/`** — dashboard metrics aggregation + OTEL export.