docs(adr): add ADR-0029, structured statement edits for raw Workshop

[e54-bot]

Summary

Proposes ADR-0029: structured statement edits for raw Workshop. It decides the write direction that ADR-0024 left open ("a typed authoring API").

• Input: a condition or action written as a rule-content-v1 list item. No second authoring format.
• Owner split: workshop-rs converts the statement to its public model and returns the checked SourceEdit (canonical text in the file's locale, indentation relative to the surrounding source). Wright composes no Workshop text.
• Surface: new editStatements operation in wright-agent/v1 (serve + MCP).
  • Addressing: rule + conditions/actions + index + insert/replace/delete.
  • Atomic: every address refers to the pre-edit program; insert takes a statements array.
  • Freshness: guarded by inputIdentity.
  • Validated through the existing validateEditTransaction path. Nothing is written by the operation.
• Scope: raw Workshop only; OverPy/OSTW input is refused with the owning implementation named.
• Edge rules:
  • replace keeps a statement's leading comment and delete removes it with the statement.
  • Inserting into an absent section creates it.
  • Optional sources works for unsaved buffers, as in validateEditTransaction.
  • Emission uses the session's resolved locale.
  • A replaced statement is visibly respelled in canonical form.
• Round-trip contract: content(parse(emit(from_content(c)))) == c, checked by workshop-rs over its corpora.

Out of scope: rule-level edits, declarations, a CLI command, source-language authoring, and the form factor of an editing view.

Why now

A read-only structured editing prototype (rule tree plus in-game-style create condition/action forms built from lookup signatures) produces correct rule-content-v1 nodes, but no operation turns a node into source text. Without this decision every client would carry its own copy of Workshop emission.

Related catalog gaps found by the same prototype are tracked separately: #781, #782, #783, wrightkit/workshop-rs#495, wrightkit/workshop-rs#496, wrightkit/workshop-rs#497, wrightkit/workshop-rs#498.

Review

Accepted by the owner after review of the open points: raw-Workshop-only scope, comment preservation on replace, visible canonical respelling, and the caller-writes edit path. The review also changed insert to take a statements array so an If, its body, and its End share one address. Documentation only; no code or behavior changes.