Anthropic prompts - consolidate <parallelizationStrategy>

[bhavyaus]

Consolidating and cleaning up the <parallelizationStrategy> block for the optimized Anthropic prompts (Sonnet 4.6, Opus 4.6, Opus 4.7). Tracking issue: https://github.com/microsoft/vscode-internalbacklog/issues/7464

What changed

• New renderAnthropicParallelizationStrategy(tools, { subagentFanOut }) helper — single source of truth for the parallel-call rule, the over-search guard, and the per-tool carve-outs (Codebase, core_run_in_terminal, execution_subagent).
• Removed the duplicated parallel-call lines from <toolUseInstructions> in both Claude46OptimizedBasePrompt and Claude47OpusPrompt — they now live exclusively in the strategy block.
• Wording strengthened from permissive ("you may parallelize... when appropriate") to imperative ("issue them in a single response... Maximize parallel tool calls where possible"), borrowed from the Claude Code system prompt.
• Opus 4.6 picks up the over-search guard ("batch the reads you have already decided you need rather than searching speculatively") that previously only Sonnet 4.6 had.
• Opus 4.7's <subagentFanOut> sub-tag is preserved verbatim, gated behind the helper's subagentFanOut: true option.

Test plan

• Sonnet 4.6 eval run completes without regression on parallel Codebase / core_run_in_terminal / execution_subagent rates (must stay at 0)
• Opus 4.6 eval run, same checks
• Opus 4.7 eval run, same checks + subagent fan-out behavior unchanged

[Copilot]

Pull request overview

Consolidates the <parallelizationStrategy> guidance for optimized Anthropic agent prompts into a single helper so that parallel tool-call rules, anti-oversearch guidance, and per-tool exceptions stay consistent across Sonnet 4.6 / Opus 4.6 / Opus 4.7.

Changes:

• Added renderAnthropicParallelizationStrategy(tools, { subagentFanOut }) as a single source of truth for parallelization + exceptions and (optionally) Opus 4.7 subagent fan-out guidance.
• Updated Claude 4.6 optimized prompts (Sonnet/Opus) to delegate their strategy block to the shared helper, and adjusted the base class hook to accept tools.
• Removed duplicated parallelization/exceptions lines from <toolUseInstructions> in Claude 4.6 optimized base and Claude 4.7 Opus prompt, keeping that guidance exclusively in the strategy block.

Show a summary per file

File	Description
extensions/copilot/src/extension/prompts/node/agent/anthropicPrompts.tsx	Introduces a shared parallelization strategy renderer and wires optimized Anthropic prompts to use it, removing duplicated guidance text.

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 1