Summary:
- add an optional worker.max_concurrent_agents_per_host setting to the
  Elixir workflow schema
- update orchestrator host selection to skip SSH hosts that are at the
  shared per-host cap and wait when all SSH hosts are full
- cover the new cap in config, scheduler, and spec documentation tests

Rationale:
- let operators bound concurrent ticket execution per SSH worker
  machine without introducing per-host bespoke config
- keep scheduling behavior predictable by treating saturated SSH hosts
  as temporarily unavailable instead of falling back to local execution
- document the feature lightly in the spec so the extension is visible
  without overspecifying implementation details

Tests:
- make all

Co-authored-by: Codex <codex@openai.com>

Summary:
- add an appendix describing the optional SSH worker extension
- clarify the execution model, scheduling notes, and operator concerns
- call out failover, workspace locality, and host-capacity behavior

Rationale:
- document the SSH extension in one place without over-specifying the
  implementation
- make the main operational tradeoffs explicit for readers and operators

Tests:
- not run (doc-only change)

Co-authored-by: Codex <codex@openai.com>

Summary:
- keep workspace.root as the configured string instead of expanding it in
  config parsing
- expand local workspace roots only at local sandbox/path use sites and keep
  ssh roots raw for worker-side ~ resolution
- update the ssh workspace tests and live e2e harness to exercise remote
  roots that begin with ~
- stabilize the orchestrator polling snapshot test under coverage timing

Rationale:
- preserve the correct ownership boundary for remote path interpretation so
  ssh workers resolve ~ using their own HOME
- avoid carrying duplicate config state such as raw_root when the consumers
  can handle expansion at the actual boundary
- keep make all green while changing the path semantics by tightening the
  affected tests

Tests:
- make -C elixir all
- cd elixir && env -u SYMPHONY_LIVE_SSH_WORKER_HOSTS LINEAR_API_KEY="$(tr -d '\r\n' < ~/.linear_api_key)" SYMPHONY_RUN_LIVE_E2E=1 mix test test/symphony_elixir/live_e2e_test.exs:128

Co-authored-by: Codex <codex@openai.com>