docs: add VS Code attach snippet, fix duplicate table, expand extension points, add batch execution design doc

[TeeYml]

docs: Fix four documentation gaps across remote debugging, README, architecture, and batch execution

Summary

This PR resolves four backlog documentation issues (I-003, I-014, I-018, I-024) identified in docs/issues/backlog-100-issues.md. All changes are documentation-only — no source code is modified.

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Changes

#935 — Add complete launch.json snippet for the VS Code attach flow

docs/remote-debugging.md covered TLS server setup and the CLI remote command but left VS Code users without a concrete attach configuration to copy. Added a new "Connect from VS Code (Attach)" subsection directly after the CLI client example. It includes a complete .vscode/launch.json snippet with all relevant fields (host, port, contractPath, entrypoint, args, token, tlsCert, tlsKey) and an inline property reference table so users can understand each field without leaving the page.

Closes #935

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#917 — Consolidate duplicated Storage Filtering pattern table in README

The README "Storage Filtering" section contained the same pattern table (balance:* / regex / exact match) in two places — once immediately after the shell examples and once orphaned below the trace JSON block (lines 200–209). Moved the table up to sit directly under the "Storage Filtering" heading where it is most useful and removed the duplicate copy below the trace output.

Closes #917

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#925 — Expand ARCHITECTURE.md Extension Points to include plugin system, remote server, and batch executor

The Extension Points section listed four items but omitted three major subsystems that have shipped since the section was written: the plugin system, the remote debug server, and the batch executor. Added three new bullet points — each with a short description of what the subsystem does, how to extend it, and links to the relevant architecture or API docs (docs/plugin-api.md, docs/architecture-plugins.md, docs/architecture-remote.md, docs/design/batch-execution-design.md).

Closes #925

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#929 — Add canonical batch execution design reference to docs/design/

The batch execution design (Rayon parallelism, result aggregation, pass/fail logic) existed only in BATCH_EXECUTION_SUMMARY.md — an implementation summary from the original feature PR, not a design document. Created docs/design/batch-execution-design.md as the canonical design reference. It covers: goals and non-goals, component diagram, key types, the Rayon work-stealing parallelism model, result aggregation logic, input file format spec, CLI and VS Code integration, performance characteristics, and extension points. Cross-linked it from docs/batch-execution.md (user guide) and ARCHITECTURE.md.

Closes #929

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