feat(hyperguild): README + Taskfile integration

Adds cmd/hyperguild/README.md (subcommands, env vars, install path)
and three Taskfile targets:

  task hyperguild:dev     — go run from source
  task hyperguild:build   — build into ./bin/hyperguild
  task hyperguild:install — go install into $GOBIN

Concludes Plan 4 of the hyperguild migration. The binary replaces
the supervisor's tier MCP and surfaces brain HTTP REST access plus
mode bootstrap to shell pipelines and ad-hoc agent prompts.

cmd/hyperguild/README.md

@@ -0,0 +1,110 @@
+# hyperguild CLI
+
+A small Go binary for tier probing, brain HTTP REST access, and
+`.mcp.json` mode bootstrap. Replaces the supervisor's `tier` MCP and
+gives shell scripts a stable interface to the brain.
+
+## Install
+
+```bash
+task hyperguild:install
+# or: go install ./cmd/hyperguild
+```
+
+The binary lands at `$(go env GOBIN)/hyperguild` (typically
+`~/go/bin/hyperguild`). Make sure that's on your PATH.
+
+## Subcommands
+
+### `hyperguild tier`
+
+Probes Anthropic and LiteLLM and reports the current operating tier.
+
+```bash
+$ hyperguild tier
+tier 1 (full-online) managed_agents=true
+
+$ hyperguild tier --json
+{
+  "tier": 1,
+  "label": "full-online",
+  "available_models": null,
+  "managed_agents": true
+}
+```
+
+Probe URLs are read from environment:
+
+| Var                   | Default                       |
+|-----------------------|-------------------------------|
+| `ANTHROPIC_PROBE_URL` | `https://api.anthropic.com`   |
+| `LITELLM_BASE_URL`    | (empty → falls through to airplane) |
+
+### `hyperguild brain query <topic>`
+
+BM25 search over the brain's knowledge + wiki entries.
+
+```bash
+$ hyperguild brain query "find -H symlink"
+knowledge/2026-05-03-find-h-not-l-symlinked-root.md  score=12  Use find -H, not find -L
+...
+```
+
+Flags:
+
+- `--limit N` — max results (default 5)
+- `--json` — emit the raw response envelope
+
+### `hyperguild brain write <type> <slug>`
+
+Reads markdown from stdin, writes a knowledge entry.
+
+```bash
+$ cat <<EOF | hyperguild brain write knowledge example-lesson
+# Example lesson
+
+## Lesson
+...
+EOF
+knowledge/example-lesson.md
+```
+
+### `hyperguild mode <cloud|client-local|sovereign>`
+
+Writes a `.mcp.json` template for the chosen operating mode.
+
+```bash
+$ hyperguild mode cloud --out ./.mcp.json
+wrote ./.mcp.json (mode: cloud)
+```
+
+Flags:
+
+- `--out PATH` — output file (default `./.mcp.json`)
+- `--force` — overwrite an existing file
+
+Modes:
+
+- **cloud** — brain MCP only. Claude Code with no routing.
+- **client-local** — brain + routing placeholder. The routing entry's
+  URL points at `koala:30310/mcp`; a `_routing_pending` field marks it
+  as awaiting Plan 6 of the hyperguild migration.
+- **sovereign** — brain only, with a `_mode_note` explaining that this
+  mode primarily uses Crush + LiteLLM and the `.mcp.json` is a Claude
+  Code fallback for emergency offline use.
+
+## Environment
+
+| Var                   | Default                  | Used by             |
+|-----------------------|--------------------------|---------------------|
+| `BRAIN_URL`           | `http://koala:30330`     | `brain *`, `mode *` |
+| `ANTHROPIC_PROBE_URL` | `https://api.anthropic.com` | `tier`           |
+| `LITELLM_BASE_URL`    | (empty)                  | `tier`              |
+
+Override `BRAIN_URL` if your brain pod is at a different Tailscale name
+or port.
+
+## See also
+
+- `docs/superpowers/specs/2026-05-03-hyperguild-cli-design.md` — full spec
+- `docs/superpowers/plans/2026-05-03-hyperguild-cli.md` — implementation plan