Add optional rejected edit memory to diffpatch prompt

[Benjamin Steenhoek (bstee615)]

Summary

Add opt-in memory.rejectedEdits model configuration option for PatchBased02.

• Record rejected suggestions only when the originating suggestion enabled rejected-edit memory
• Keep rejected suggestions separate from normal NES diff history in a bounded compact-hunk buffer
• Annotate rejected edit-history hunks with <|rejected/|> and explain the annotation in the prompt

Rejection annotations are added to edit_diff_history as standalone entries. Toy example:

<|edit_diff_history|>
--- src/auth.ts
+++ src/auth.ts
@@ -12,1 +12,1 @@
-  if (user.isAdmin) {
+  if (user.role === 'admin') {

--- src/auth.ts
+++ src/auth.ts
@@ -18,1 +18,1 @@ <|rejected/|>   <-- This tag marks the entry as a rejection
-  return true;
+  return user.permissions.includes('deploy');

--- src/auth.ts
+++ src/auth.ts
@@ -18,1 +18,1 @@
-  return true;
+  return user.permissions.includes('read');
<|/edit_diff_history|>

// Addition to the postscript instructs the model what to do with rejections
... Adhere meticulously to the diff format. Edit history hunks whose header ends with \`${REJECTED_EDIT_TAG}\` are previous suggestions the developer rejected; avoid repeating them unless later context makes them clearly appropriate.

The rejection buffer retains at most three entries and 3,000 characters per entry. It stores only the changed line hunks. Adds an extra property sequence to preserve the order of edits and rejections.

TODOs:

• Tune the amount of context given with rejected edits
• Make rejected edits more token-efficient (e.g. by merging them with existing diff history entries rather than adding standalone entries)

Validation

• Lint + compile passes
• Added test cases for new prompt options and baseline
• STests experiments show 33% reduction in bad repeats
• STests experiments show that after 1-3 user edits, the deterministic local cache prevents bad repeats only 1/3 of the time

[Copilot]

Pull request overview

Adds opt-in rejected-edit memory to PatchBased02 prompts.

Changes:

• Captures up to three compact rejected edits.
• Merges rejected and normal history chronologically with annotations.
• Propagates model attribution through requests, caches, and telemetry.

Show a summary per file

File	Description
extensions/copilot/src/platform/inlineEdits/test/common/xtabPromptOptions.spec.ts	Tests configuration validation.
extensions/copilot/src/platform/inlineEdits/common/workspaceEditTracker/nesXtabHistoryTracker.ts	Stores bounded rejected-edit history.
extensions/copilot/src/platform/inlineEdits/common/statelessNextEditProvider.ts	Carries history and attribution.
extensions/copilot/src/platform/inlineEdits/common/dataTypes/xtabPromptOptions.ts	Defines the memory option.
extensions/copilot/src/extension/xtab/test/node/diffHistoryForPrompt.spec.ts	Tests annotated history rendering.
extensions/copilot/src/extension/xtab/test/common/promptCrafting.spec.ts	Tests prompt integration.
extensions/copilot/src/extension/xtab/node/xtabProvider.ts	Enables memory for PatchBased02.
extensions/copilot/src/extension/xtab/common/promptCrafting.ts	Adds rejected history to prompts.
extensions/copilot/src/extension/xtab/common/diffHistoryForPrompt.ts	Renders and budgets rejected hunks.
extensions/copilot/src/extension/inlineEdits/test/node/nextEditProviderTelemetry.spec.ts	Updates telemetry expectations.
extensions/copilot/src/extension/inlineEdits/test/node/nextEditProviderSpeculative.spec.ts	Updates speculative telemetry fixture.
extensions/copilot/src/extension/inlineEdits/test/node/nextEditProviderCaching.spec.ts	Tests rejection attribution through cache.
extensions/copilot/src/extension/inlineEdits/test/node/nextEditCacheRebase.spec.ts	Updates rebase telemetry fixture.
extensions/copilot/src/extension/inlineEdits/test/node/nextEditCacheCursorDistance.spec.ts	Updates cursor-distance fixture.
extensions/copilot/src/extension/inlineEdits/test/node/nesXtabHistoryTracker.spec.ts	Tests bounds and compaction.
extensions/copilot/src/extension/inlineEdits/node/nextEditResult.ts	Exposes originating memory state.
extensions/copilot/src/extension/inlineEdits/node/nextEditProvider.ts	Records qualifying rejections.

Review details

• Files reviewed: 17/17 changed files
• Comments generated: 1
• Review effort level: Medium

done