v0.5.0 — install into every agent rungraph can read

rungraph mcp --install now installs into every agent rungraph can read — Claude Code, Codex, Hermes Agent and opencode — not just Claude Code. This release has a breaking change to the --install / --check JSON output.

• src/clients.js is the one MCP client table: how rungraph registers with each agent and how it reads back whether it is there. Keyed to ADAPTERS, and tests/clients.test.js fails CI if an adapter has no entry, so a fifth adapter cannot land without deciding how it installs.
• --install registers with every detected agent (--client <name>|all to target). All four delegate to the vendor's own CLI — claude mcp add, codex mcp add, hermes mcp add, opencode mcp add — so rungraph never edits an agent's config file. A failed delegation prints that client's config block instead of dead-ending.
• --check reports one row per detected agent and passes when at least one is wired up.
• Launch resolver. npx rungraph mcp --install used to write an absolute path into ~/.npm/_npx, a cache npm garbage-collects, after which the tools silently vanished. It now writes npx -y rungraph mcp from an npx cache and rungraph mcp from a global install.
• serve nudge. A one-line hint to install the MCP server until an agent has actually handshaked (RUNGRAPH_NO_NUDGE=1 silences it).
• Every vendor behaviour was probed against the real CLI; five claims in the design spec were falsified by probing, including that opencode could not be delegated to (it has an undocumented -- passthrough).

Breaking:

• Bare --install used to mean --client claude; it now registers with every detected agent.
• --install --json moves per-client fields into clients[]; installed is now a count and wrote is gone.
• --check --json no longer has a check named "registered with claude".
• The README's Hermes one-liner is retired — it silently no-opped when scripted.