Align the interop docs with the settled #198 pilot decisions #316

First unchecked P0 box of #198. The four design decisions are settled and recorded on the issue (2026-10-18 comment: A-first, single-owner phase 1, fixture-task limits, driver-owned supervised OpenCode child). Two interop docs still contradict them:

docs/interop/opencode-pilot.md:

• "two independent platform owners … this trial is cross-owner traffic … applicable cross-owner gates remain required" vs decision 2 (single-owner phase 1; Team mode via groups: task layer step 1 - responsible-owner authority, FLYBOT-TASK envelope, workBotId #149/[Team] Gate cross-owner agent routes by per-Bot grants (default deny; superseded the publication gate) #51/[Team] Recover task handoffs without duplicate work #55–[Team] Verify the real two-human team pilot end to end #58 off the critical path).
• The retry-function text-analysis task with "no repository checkout, … shell command, code write" vs decision 3 (the isolated fixture code task; tools = file edit + run tests, no network).
• "the operator starts/stops a dedicated OpenCode server" vs decision 4 (the FlyBot driver owns a supervised child process).

docs/interop/room-participants.md:

• "An OpenCode participant also needs an operator-controlled installation binding" vs decision 4.

Acceptance:

• Both docs state the settled decisions and stop contradicting them; the DM/offline experiment's own constraints (Bot Social same-owner friendship rejection, distinct synthetic owners in the mock) remain intact where they are still true.
• The still-valid parts of the v1 contract (codec, journal, budget, projection, evidence levels) are preserved unchanged.
• npm run verify green (arch-docs: docs/interop/ is not an owned path; no subsystem doc change required).