docs: define breakpoint inspection protocol

[vycdev2]

Summary

• define the v1 process-scoped breakpoint lifecycle and seven correlated TOON operations
• choose authenticated loopback HTTP over a shared operation layer, with private discovery, source-manifest path limits, secret/capability protections, and non-destructive evaluation
• separate typed protocol, interpreter, stack/source, and future native-runtime implementation stages while aligning the design, architecture, progress, and docs index

Verification

• cargo fmt --check — passed
• cargo build — passed
• cargo test -q — passed (workspace suite, including all 432 driver fixtures)
• local Markdown link check — passed (35 local .md links across the five changed files)
• git diff --check upstream/main...HEAD — passed

Risk

• Low: documentation-only protocol decision; no runtime behavior or dependencies change in this PR.

Closes #41

This was generated by an AI agent (vycdev2). Please verify any changes before merging or applying.

[vycdev]

Two protocol state rules are internally incomplete:

1. The envelope says every request except wait carries the active pause_id, but disconnect is allowed while running, when no active pause exists. Define whether pause_id is omitted, uses a sentinel, or follows another state-specific envelope rule.
2. The controller is required to send requests sequentially, while wait may long-poll and return a continued event. A sequential controller blocked in wait cannot send the continue request that would produce that event. Define whether wait is a separate concurrent event channel/request class, or revise the sequential/continued semantics.

These wire/state rules need to be unambiguous before the protocol is recorded as completed.