* fix(checkout): dry runs change nothing; switching ends a merge (#236)

A dry-run Extract still called LoadVFile(rid, clear=true) and finalizeExtract, replacing the current version's vfile rows (pending adds, renames, merge state) and moving vvar to the target. A dry-run Update still ran finalizeUpdate, with the same effect.

Extract now lists the target's files from its manifest (resolveFiles) instead of reading them back from vfile, so a dry run never loads them; only a real extract replaces vfile and records the version. Update skips finalizeUpdate on a dry run.

finalizeExtract also clears vmerge, as fossil's checkout does: a forced switch used to leave a merge record that would give the next commit a bogus merge parent.

* fix(checkout): forced extract starts fresh; re-extract keeps a merge (#236)

Two gaps against fossil's checkout found in review:

- A forced extract dropped only other versions' vfile rows (LoadVFile keeps the target's), so re-forcing the current version left a pending rename's two names on disk and in vfile, and a removed file restored but still marked deleted. fossil checkout --force deletes every row first; replaceFileList now does the same when Force is set. - Extract cleared vmerge on every completed run. fossil's checkout returns early when the version does not change and Force is off, keeping a pending merge; finalizeExtract now ends the merge only for a switch or a forced extract.

* refactor(checkout): finalizeExtract reads the prior version itself (#236)

Only the final step needs the version being replaced, and nothing changes vvar before it, so finalizeExtract reads it there. A dry run no longer calls Version at all, and Extract drops to 64 lines. check-in: 139d426384 user: [email protected] tags: trunk