Don't mutate the caller's managed map in BuildPlans

[Soph]

Problem

BuildPlans passed the caller's managed map straight into addPruneCandidates, which inserts prune candidates. So a --prune plan mutated a map the caller still owns (and may reuse). BuildReplicationPlans already copied defensively, so the two diverged.

Fix

Copy managed inside the if cfg.Prune block in both functions — that's the only place the map is mutated, so neither touches the caller's map, both stay symmetric, and the copy is skipped entirely when not pruning.

Tests

TestBuildPlansDoesNotMutateManagedMap runs a --prune plan with a stale target ref, confirms it's planned for deletion (prune actually ran), and asserts the caller's managed map is unchanged (the prune candidate landed only in the copy).

🤖 Generated with Claude Code

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Note

Low Risk
Localized defensive copy in plan builders with a regression test; behavior for prune/delete plans is unchanged aside from fixing unintended map mutation.

Overview
BuildPlans with --prune no longer mutates the caller’s managed map. Prune candidates from addPruneCandidates are applied only on a copyManagedTargets copy, matching BuildReplicationPlans.

BuildReplicationPlans now copies managed only when cfg.Prune is set (it previously copied on every call). Both builders share the same rule: no copy when not pruning, copy before the only mutation when pruning.

Adds TestBuildPlansDoesNotMutateManagedMap to assert a stale ref gets a delete plan while the caller’s managed map stays length 1 with no leaked prune entry.

^{Reviewed by Cursor Bugbot for commit cf4957c. Configure here.}