perf(wave2): dynamic config arrays, flat dwindle tree, dual client arrays
Wave 2 changes:
- Dynamic Config arrays with geometric growth (cap=16, 2x growth)
→ saves ~2.5 MB heap for typical configs vs fixed 128-entry arrays
- Proper deep-copy protocol in on_config_reload/do_reload (free old, move new, zero source)
- Flat DwindleTree array with int children[2]/parent indices
→ eliminates pointer chasing, contiguous allocation, iterative two-pass recalc
- Lazy per-tag allocation (DwindleTree.nodes starts NULL, allocates on first use)
- Dual client_arr + fstack_arr arrays alongside wl_list/fstack for cache-friendly iteration
→ arrange() and focustop() use array scan instead of linked-list pointer chase
- All arrays maintain size-tracking (nclients, nfstack) for bounds checking
- Zero-warning build with clang -Werror -Wpedantic
huntedbytheirs
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