Rewrite the planner as the tactician

Part of #16. The tool is named after a grand admiral whose whole character is studying his opponents before engaging; the planner prompt should lean into it. Convictions about decomposition (interfaces first, no shared files, doubt the ticket's framing, a single-task plan is a welcome outcome) written as souls/tactician.md and mapped via the #19 mechanism, with memory of past campaigns arriving through #18.

• Draft the soul as falsifiable convictions with things it deliberately does not care about
• Map planner to tactician in runners.toml
• Compare a few plans before and after on the same tickets; the width gate stats in state.json are the measure

After phase 2 of #14: the planner must not change mid-trial.

Agent brief (phase 2 constraint)

This ticket is trial fodder while phase 2 of #14 runs, so it must land INERT: write souls/tactician.md following souls/README.md (falsifiable convictions about decomposition, things it deliberately ignores, plain harness-agnostic text, no tool names) and add tests asserting the file exists and stays plain text if useful, but DO NOT map it in the [personas] table of runners.toml. The mapping flips after phase 2 concludes. Acceptance: soul file committed, make test and make lint green, [personas] untouched.

Start by reading souls/README.md and inspecting the existing soul files and relevant tests. Add souls/tactician.md as plain, harness-agnostic text with falsifiable decomposition convictions and explicit non-goals, then run make test and make lint. Leave the [personas] table in runners.toml unchanged; done means the soul is committed and both checks pass.