#1167 Surface the bundled deno path in the first-loaded extension guide + expose it via CLI

Problem

Extension test/lint commands need the bundled deno binary at ~/.swamp/deno/deno. That path is only documented in on-demand deeper references (extension/reference.md, quality/templates.md, troubleshooting/health-checks.md). The first-loaded guide, extension/guide.md, references deno (deno doc --lint) but never gives the path.

Result: in nearly every extension-writing session, the agent has the need surfaced up top and the answer buried a reference-load away, so it falls back to filesystem guessing (which deno, find ~/.swamp, …) instead of reading the docs. It usually finds the right path — by luck, not instruction — which is wasted work and a violation of the skill's own "use the routing table, not memory" rule.

Proposed solution

1. Add the pinned path to extension/guide.md's Quick Reference table:

   • Type-check -> ~/.swamp/deno/deno check <file>
   • Run tests -> ~/.swamp/deno/deno test extensions/models/foo_test.ts

   Plus a one-line note near Import Rules: "Bundled deno lives at ~/.swamp/deno/deno (not on PATH) — invoke by full path."

2. Expose the resolved path via CLI so it's discoverable without docs: a field in swamp doctor extensions --json, or a small swamp extension env. This survives version/platform path changes.

Alternatives considered

• Rely on existing deeper references — insufficient; empirically not loaded before the agent resorts to searching.

Environment

• Recurs across essentially every extension write/test session. swamp skill docs as of 2026-07-15; bundled deno at ~/.swamp/deno/deno with adjacent .version.