## Why

The lean profit-loop review showed one clear next question: the only subtype worth pursuing is `mid_zone_very_weak_b1`, and its current probe path likely fails because the reentry is clipped too early by the default glued take-profit logic.

We do not need a broad sell-system rewrite. We need one narrow, shadow-only exit experiment that asks:
- if a repaired mid-zone followthrough reentry is still structurally healthy,
- should it be allowed to survive the first mild `kdj_sell` instead of being cut by `knife_take_profit_2_glued`?

## What Changes

- Add a narrow helper for followthrough-reentry-specific `kdj_only` exit hold.
- Add config gates for this exit treatment, all default-off.
- Add a new shadow branch:
- `alpha_first_glued_followthrough_mid_exit_probe`
- Add a focused review script comparing:
- RC1 base
- original mid followthrough probe
- new mid exit probe
- Add a regression test pinning the new branch fixture.
- Expose the new branch in daily pipeline outputs only.

## Impact

- Affected code: config, branch config, strategy sell path, daily pipeline, new review script, new test, new OpenSpec pack.
- Runtime impact: negligible.
- Governance impact: none to RC1 default path.