Classify save failures as transient or terminal (`transient-error?`
over the repo retryable types plus `:invalid-save-response`).
Transient failures keep the head commit queued under a new `:retrying`
status and resend it with backoff (2s/8s/20s, then terminal):
stamp rotation reuses the same `:commit-id`, the in-flight guard
prevents double-sends, and episode tokens silence stale timers.
One tagged reconnect notice per episode (hidden on save and on
terminal failure, silent recovery) plus a `:retrying` save-indicator
state; the browser `online` event and new edits resume the episode.
Terminal failures keep the exact `:error` path. Covers tasks 4, 6
and 7 with 31 persistence tests; updates the persistence memory.
Relates to #11724
AI-assisted-by: muse-spark-1.3-contributor
* ✨ Adds static dispatch safe stubs in tests
* 🐛 Fix shapesColors metadata key to match ColorShapeInfo
* 🐛 Fix CommentThread.remove rejecting the owner's own threads
* 🐛 Fix page.removeCommentThread throwing on a spurious Promise
* ✨ Implement ShapeBase.swapComponent in the plugin API
* ✨ Expose File.revn in the plugin API
* 🐛 Fix FileVersion.createdAt calling Luxon method on a js/Date
* 🐛 Fix plugin font/typography application to text and ranges
* 🐛 Default plugin overlay interaction position for non-manual types
* 🐛 Fix plugin interaction setters passing an id-only shape
* 🐛 Fix grid addColumnAtIndex rejecting valid track types
* 🐛 Expose libraryId on library color/typography/component proxies
* ✨ Implement LibraryTypography.setFont in the plugin API
* 🐛 Fix typography.applyToTextRange reading unexposed range bounds
* 🐛 Fix utils.geometry.center argument mismatch
* 🐛 Fix localStorage.removeItem calling getItem
* 🐛 Fix shape backgroundBlur proxy key casing
* 🐛 Report boolean shape type as 'boolean' in the plugin API
* 🐛 Return the resulting paths from plugin flatten
* 🐛 Make plugin z-order methods act on the target shape
* 🐛 Make is-variant-container? return a boolean
* ✨ Implement Group.isMask in the plugin API
* 🐛 Return a shape proxy from TextRange.shape
* 🐛 Return the duplicated set from TokenSet.duplicate
* 🐛 Fix theme addSet/removeSet reading set name with a keyword
* 🐛 Accept string fontFamilies token value in the plugin API
* 🐛 Fix combineAsVariants ignoring the passed component ids
* 🐛 Fix board removeRulerGuide ignoring its argument
* 🐛 Fix board guides setter schema and parser
* 🐛 Avoid 0-byte allocation when syncing empty grid tracks
* 🐛 Validate grid track indices in the plugin API
* 🐛 Return null for empty input in group() and centerShapes()
* 🐛 Return TokenTypographyValue[] from a typography token's resolvedValue
* 🐛 Return TokenShadowValue[] from a shadow token's resolvedValue
* 🐛 Return string[] from a fontFamilies token's resolvedValue
* 🐛 Clear mutually-exclusive reps when setting LibraryColor gradient/image
* 🐛 Add readonly tags to types, deprecate Image type
* 📚 Update plugins changelog
