Four non-overlapping algorithmic complexity reductions in hot paths.
(Streaming-reveal throughput is owned separately by #3843.)
1. session/session-manager.ts pathTo: O(n^2) branch.unshift() leaf->root
walk -> O(n) push + single reverse(). Hot path (5-10x/turn via getBranch).
2. edit/streaming.ts extractAddedLines: O(n^2) progressive string
concat per streaming tick -> array push + single join.
3. edit/modes/patch.ts: collapseConsecutiveSharedLines O(n*m) filter
+ includes -> Set (O(n+m)); collapseRepeatedBlocks O(n^3) with
per-iteration slice allocations + every() -> index arithmetic with
a single shared.has() guard. Semantics preserved.
Honorable: tui/src/utils.ts replaceTabs reallocated
" ".repeat(DEFAULT_TAB_WIDTH) every call -> hoisted TAB_SPACES const.
oldschoola
d9bc5ca405