docs: rewrite README with install + commands + canonical layout + conflict resolution

README.md

@@ -1,13 +1,105 @@
 # harness-sync
 
-Sync skills, agents, MCP, and LLM endpoints across multiple LLM harnesses
+One canonical source of truth for skills, agents, MCP servers, LLM endpoints, and global instructions across multiple LLM harnesses. Edit once at `~/.config/harness-sync/`; propagate everywhere.
-(claude-code, crush, kilo, opencode, goose, cagent, zed).
 
-Canonical config lives in `~/.config/harness-sync/` (git-tracked). Run
+## Supported harnesses
-`harness-sync apply` to propagate.
 
-See `docs/superpowers/specs/2026-05-23-harness-sync-design.md` for design.
+| Harness | Config path | What harness-sync writes |
+|---|---|---|
+| claude-code | `~/.claude/` | `skills/` (symlink), `agents/` (symlink), `CLAUDE.md`, `settings.json` `mcpServers` (merged) |
+| crush | `~/.config/crush/` | `skills/` (symlink), `crush.json` `providers`/`default_model`/`mcp` (merged) |
+| kilo | `~/.config/kilo/` | `agent/` (symlink), `kilo.json` `model`/`mcp` (merged) |
+| opencode | `~/.config/opencode/` | `opencode.jsonc` `provider`/`model`/`mcp` (merged), `AGENTS.md` |
+| goose | `~/.config/goose/` | `config.yaml` `GOOSE_PROVIDER`/`GOOSE_MODEL`/`extensions` (merged) |
+| cagent | `~/.config/cagent/` | starter `default.yaml` (per-run config) |
+| zed | `~/.config/zed/` | `settings.json` `agent`/`context_servers` (merged — other keys preserved) |
 
-## Build
+Adding a new harness: drop a Go package under `internal/adapters/<name>/` implementing `adapter.Adapter`, register it in `cmd/harness-sync/main.go`.
 
-    make build && make install
+## Install
+
+```bash
+make build && make install   # installs to ~/.local/bin/harness-sync
+```
+
+## First run
+
+```bash
+harness-sync detect          # see which harnesses are installed
+harness-sync init            # pick which to import from; canonical tree created at ~/.config/harness-sync/
+harness-sync apply           # propagate canonical to all detected harnesses
+```
+
+`init` opens an interactive multi-select of detected harnesses. Use `--no-prompt` to import from all, or `--from claude-code,crush` to be explicit.
+
+## Day-to-day
+
+```bash
+harness-sync show              # list files each adapter would write
+harness-sync diff              # apply --dry-run shorthand
+harness-sync apply             # propagate canonical
+harness-sync apply crush       # propagate to one harness only
+harness-sync profile use work  # switch active profile and reapply
+harness-sync rollback 1        # revert last apply via git revert
+harness-sync adapter list      # print registered adapters
+```
+
+## Canonical layout
+
+```
+~/.config/harness-sync/
+├── config.yaml                # enabled_harnesses, active_profile
+├── profiles/
+│   ├── home.yaml              # gateway URL + token + model allowlist + upstreams
+│   └── work.yaml
+├── instructions/
+│   ├── global.md              # rendered to CLAUDE.md / AGENTS.md / etc.
+│   └── per-harness/<name>.md  # optional override
+├── skills/<name>/SKILL.md     # markdown + frontmatter; symlinked into harnesses that accept it
+├── agents/<name>.md           # markdown + frontmatter
+├── mcp.yaml                   # canonical MCP server registry
+├── state/<harness>/...        # last-rendered snapshots (git-tracked, do not hand-edit)
+└── backups/                   # pre-apply backups; git-ignored
+```
+
+The whole tree is a git repository. Push it to a private remote for cross-machine sync.
+
+## Profiles
+
+A profile bundles the LLM stack. Switching profiles re-renders every harness's LLM config in one command.
+
+```yaml
+# profiles/home.yaml
+name: home
+gateway:
+  url: https://gateway.lan
+  token: dummy-local-token
+  default_model: claude-sonnet-4-6
+upstreams:
+  - name: anthropic
+    api_key: ${ANTHROPIC_API_KEY}
+  - name: openai
+    api_key: ${OPENAI_API_KEY}
+models:
+  - id: claude-sonnet-4-6
+    alias: sonnet
+  - id: claude-opus-4-7
+    alias: opus
+```
+
+Secrets use `${VAR}` for env-var substitution at render time. The dummy gateway token may be plaintext (it has no value if leaked); real provider keys must be env-var references.
+
+## Conflict resolution
+
+`apply` performs git-style three-way merge on every rendered file. The base is the previous render snapshot from `state/<harness>/`; "ours" is the new render; "theirs" is the current target file. When the merge is clean, the target is updated. When it conflicts, harness-sync writes the merged-with-markers result next to the target as `<file>.rej`, leaves the original file untouched, and exits non-zero. Resolve the conflict (edit the target, delete `.rej`), then run `apply` again.
+
+The same canonical repo holds the state snapshots. `rollback N` calls `git revert` on the last N commits and reapplies.
+
+## Design and implementation
+
+- Design: [`docs/superpowers/specs/2026-05-23-harness-sync-design.md`](docs/superpowers/specs/2026-05-23-harness-sync-design.md)
+- Plan: [`docs/superpowers/plans/2026-05-23-harness-sync.md`](docs/superpowers/plans/2026-05-23-harness-sync.md)
+
+## License
+
+Same as the surrounding repo.