* fix(checkout): refuse to load a version with missing content (#231)

LoadVFile wrote a vfile row with rid=0 for each file whose content the repo does not hold (a phantom, or a delta on one), as a partial sync leaves it. In fossil's vfile rid=0 means "added", so those rows were indistinguishable from pending adds, and Extract then panicked in content.Expand(0) trying to write them.

LoadVFile now does what fossil's checkout does: it resolves every file first and refuses the version, naming up to ten missing files and wrapping errMissingContent, before changing vfile at all. It no longer returns a missing count, which no caller used.

Create is the one caller that tolerates the refusal. A tip that a partial sync has not finished is no reason to fail CreateCheckout: the caller may be about to extract an older, complete version (EdgeSync's ExtractTo). vfile then stays empty instead of claiming files the repo cannot produce. Create's environment defaulting, shared with Open, moves to resolveEnv, and the initial load to loadInitialVFile.

Tests cover the refusal (vfile untouched, files named), Extract leaving the checkout as it was, Create on a partial tip followed by Extract of a complete version, and parity with the fossil binary, which refuses the same repository with "missing content".

* fix(checkout): refuse missing content in Update before writing (#231)

Update wrote changed files to disk and only then reloaded vfile, which now refuses a version with missing content. A target sharing a missing file with the current version (its content is never read, because it does not change) could therefore leave disk on the target while vvar and vfile stayed on the old version. Like fossil's update, Update now resolves the target's content before writing anything, through resolveFiles, the resolution step split out of LoadVFile.

Update moves its target selection into updateTarget, reuses Extract's checkinTime, and builds its result through sortedUpdateResult, bringing it under 70 lines. Create now reports a tip it could not load to the observer instead of tolerating it silently.

* fix(checkout): report Update refusals to observers; tighten checks (#231)

The missing-content check in Update moves after ExtractStarted, so a refused update still reaches observers as an ExtractCompleted carrying the error, as other Update failures do. A negative target from the public UpdateOpts is an error, not a panic. resolveFiles errors carry their own prefix instead of LoadVFile's.

Adds the entry and exit assertions the new helpers were missing, a compile-time check on missingNamesMax, and wraps lines over 100 columns; tests check Version's error instead of discarding it. check-in: a317896683 user: [email protected] tags: trunk