fix(sdk): invalidate stale screen asset URLs on edit and prioritize revision screens (#361)

[davideast]

Summary

Resolves the SDK-side root causes of #361 (Tier 2 — Part 2 of 3 in stack, stacked on #377).

When a caller runs the iterative design loop (generate $\rightarrow$ getHtml $\rightarrow$ edit $\rightarrow$ getHtml), two SDK-level cache/ordering issues caused edited.getHtml() to return unchanged pre-edit HTML:

1. Stale htmlCode / screenshot cache retention on in-place edits: Calling await screen.getHtml() caches this.data.htmlCode.downloadUrl on the Screen instance in EntityManager. When screen.edit() returned the updated Screen without an inline htmlCode.downloadUrl, mergeEntityData kept the pre-edit htmlCode.downloadUrl, causing edited.getHtml() to short-circuit on the cache and return the pre-edit URL without calling get_screen.
2. Original vs. revision ordering in outputComponents: When edit_screens returns both the original selectedScreenIds screen (s1) and a newly minted revision screen (s2) in outputComponents[].design.screens[], Generation.first (edited.getHtml()) pointed to s1 (original) instead of s2 (edited revision).

Changes

• EntityManager.prototype.invalidateScreenAssets(projectId, screenId): Clears cached htmlCode and screenshot fields on mutated screens before EntityManager.resolve merges the edit_screens / apply_design_system response.
• StitchToolClient.prototype.reconcileEditedScreens(): Automatically invalidates stale asset URLs for selectedScreenIds and orders newly minted revision screens ahead of original selectedScreenIds in outputComponents[].design.screens[].