WIP: Add response optimisation for list_ tools

[kerobbi]

Summary

Adds a response optimisation package that reduces token usage in list_ tool responses by applying six strategies: nested object flattening, URL elimination, zero-value elimination, whitespace normalisation, collection summarisation, and fill-rate filtering.

Two config mechanisms, preservedFields and collectionFieldExtractors, control which fields are exempt from optimisation and how nested collections are reduced.

Why

Current JSON responses are token heavy.

What changed

• Added pkg/response/optimize.go - optimisation pipeline with two config mechanisms (preservedFields and collectionFieldExtractors)
• Added tests covering all strategies and config interactions
• Wired response.MarshalItems into list_pull_requests (remaining tools in progress)

MCP impact

• No tool or API changes
• Tool schema or behavior changed
• New tool added

Prompts tested (tool changes only)

• WIP

Security / limits

• No security or limits impact
• Auth / permissions considered
• Data exposure, filtering, or token/size limits considered

Tool renaming

• I am renaming tools as part of this PR (e.g. a part of a consolidation effort)
  • I have added the new tool aliases in deprecated_tool_aliases.go
• I am not renaming tools as part of this PR

Note: if you're renaming tools, you must add the tool aliases. For more information on how to do so, please refer to the official docs.

Lint & tests

• Linted locally with ./script/lint
• Tested locally with ./script/test

Docs

• Not needed
• Updated (README / docs / examples)