v1.2.4: kit payload v2 + sequential worker dispatch

The kit learns from a real job: sequential dispatch, honest worker reports and a built-in way to verify it is working.

A deep re-audit against Anthropic's coordinator-pattern cookbook, plus one big real-world build, turned into a second generation of the flagship kit's delegation policy.

Features

• Kit delegation policy v2 - the plan-big-execute-small fragment now teaches dispatch craft: a dispatch names the files, the exact change, the constraints and the test to run, so the worker executes instead of re-deriving context. It prefers fewer, larger chunks because every dispatch pays a fixed overhead. A dispatch that dies with an error is re-dispatched unchanged instead of absorbed into the expensive main loop. Plans build on scout-verified findings, not on memory. Each rule ports a caveat from Anthropic's cookbook.
• Worker reports open with a status - done as dispatched, done with deviations, partial or blocked. Large changes report per-file line ranges instead of pasting whole diffs, so the planner's context stays lean and review happens in git diff.
• cleat kit show tells you how to verify routing - after a heavy session /usage should show the bulk of tokens on the worker model. A heavy session showing only your session model means delegation is not happening.

Fixes

• Parallel worker dispatch is out - launching several workers in one message scrambled briefs, spawned duplicates and clobbered files on a real build. The failure classes match open upstream Claude Code bugs (duplicated parallel fan-out, concurrent edit clobbering), unfixed as of this release. The fragment now dispatches one worker at a time: dispatch, review, then dispatch the next. The ban lifts once upstream ships deduplication and edit protection.
• The confirm screen stops overstating scout - scout structurally lacks Edit and Write but its Bash stays inspection-only by instruction, so the screen now says read-only by contract instead of stating it flat. When your own agent shadows a kit agent by name, the collision warning now says the kit's policy will steer your agent with its model and its tools.

Changes

• 1447 (+8) behavioral tests across 47 files - every new fragment rule, the worker report contract, the sequential-dispatch ban, the confirm-screen wording, the collision note and the kit show verification note each pinned by a test
• 298 (+8) mutations caught, 0 missed, 0 skipped
• README copy polish