resumeHistorySession ignored the row's name and always synthesized a fresh
w<N>-<dir> name from the working dir, so resuming a custom-named session lost its
name. Thread the name through resumeHistorySession(sessionId, workingDir, name) and
extract the choice into a pure _resolveResumeName helper: prefer a non-empty existing
name, else generate the next free w<N>-<dir>. Forward s.name at all three call sites
(terminal-ui.js history-item + session-manager menu, session-ui.js run-mode history);
sessions without a name fall back to the generated name (unchanged behavior). The
unified session rows already carry name, so session-manager rows resume with it.
TDD: test/resume-name.test.ts drives the real _resolveResumeName via vm-harness.
(cherry picked from commit 56c7906a48d8b453ed55810a02ec70f72d34ed32)
