Rewrite the integrator as the fixer

Part of #16. The unglamorous character: suspicious of both sides of a conflict, never adds features, treats a semantic conflict as evidence the plan was wrong rather than something to paper over. Written as souls/fixer.md and mapped via #19.

• Draft the soul with explicit anti-goals (no feature creep, no silent behaviour changes while resolving)
• Map integrator to fixer in runners.toml
• Judge on integrator_attempts and check outcomes in the ledger

After phase 2 of #14 and after #24 (the tactician).

Agent brief (phase 2 constraint)

Trial fodder while phase 2 of #14 runs, so it must land INERT: write souls/fixer.md following souls/README.md (suspicious of both sides of a conflict, never adds features, treats a semantic conflict as evidence the plan was wrong; include explicit anti-goals), plain harness-agnostic text. DO NOT map it in the [personas] table of runners.toml; the mapping flips after phase 2. Acceptance: soul file committed, make test and make lint green, [personas] untouched.

Start with souls/README.md, then draft souls/fixer.md using the stated fixer traits and explicit anti-goals. Run make test and make lint; done means the soul file is committed, both checks pass, and the [personas] table in runners.toml remains untouched.