feat(symphony): tracker-agnostic orchestrator plugin

Sketch of a Claude Code port of openai/symphony — a daemon-style
orchestrator that polls an issue tracker, dispatches isolated worker
agents per issue, and reconciles state across ticks. Tracker-agnostic
by design: the project's CLAUDE.md documents how to talk to whatever
tracker is in use (GitHub Issues, Gitea, tracker CLI, Linear, etc.);
the plugin reads those instructions rather than shipping per-tracker
adapters.

Includes:
- /symphony-init for first-time setup (detects gh/gitea/tracker, writes
  the tracker section into project CLAUDE.md, drops WORKFLOW.md, offers
  to schedule the tick)
- /symphony-tick fired by /schedule cron entries (idempotent, silent,
  never prompts)
- per-issue worker agent in isolated worktrees
- on-disk state in .symphony/state.json (survives cron cold starts)

Known divergences from the spec are documented in the plugin CLAUDE.md
(no streaming agent telemetry; no codex.* knobs; hooks run inside the
worker rather than the orchestrator).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

symphony/templates/WORKFLOW.md

@@ -0,0 +1,66 @@
+---
+# Pick the tracker your project uses. Symphony does not care which —
+# it asks the project's CLAUDE.md how to talk to it.
+#
+#   github  — `gh` CLI
+#   gitea   — gitea MCP server
+#   tracker — local `.tracker/` CLI (see tracker-usage skill)
+#   linear  — Linear MCP / GraphQL
+#   <yours> — anything, as long as your CLAUDE.md documents it
+tracker:
+  kind: github
+  active_states:   [open]
+  terminal_states: [closed]
+
+polling:
+  interval_ms: 60000
+
+workspace:
+  root: ~/.symphony/workspaces
+
+hooks:
+  after_create: |
+    git fetch origin
+    git checkout -b "{{ issue.branch_name | default: issue.identifier }}"
+  before_run: |
+    # project-specific install/setup
+    test -f package.json && npm install --silent || true
+    test -f pyproject.toml && uv sync || true
+  after_run: |
+    # advisory — never blocks the tick
+    true
+  timeout_ms: 120000
+
+agent:
+  max_concurrent_agents: 3
+  max_turns: 30
+  max_retry_backoff_ms: 600000
+  max_concurrent_agents_by_state:
+    "in progress": 2
+---
+
+You are working on issue **{{ issue.identifier }}** — {{ issue.title }}.
+
+{% if attempt %}This is retry attempt {{ attempt }}. Review prior worktree commits and
+pick up where the last attempt stopped.{% endif %}
+
+## Issue body
+
+{{ issue.description }}
+
+## Labels
+
+{{ issue.labels | join: ", " }}
+
+## Your job
+
+1. Implement the change on branch `{{ issue.branch_name | default: issue.identifier }}`.
+2. Add or update tests covering the new behavior. Run them.
+3. Commit referencing `{{ issue.identifier }}`.
+4. Push the branch and open a PR.
+5. Comment on the issue with the PR link, then transition the issue to a "review" state.
+   Use the commands documented in this project's CLAUDE.md under the issue tracker
+   section — the plugin does not know your tracker's quirks.
+
+If you cannot finish in your turn budget, leave a status comment on the issue summarizing
+progress and stop. Do not transition state.