[M11 contract] Align deferred .opy surface with corpus evidence

[Teakowa]

Parent: #82
Depends on: #81

Goal

Update the native .opy support matrix so the documented deferred surface matches the real-world constructs observed in M11 phase 1, with no behavior changes.

Scope

• Document currently unsupported line continuation syntax, postfix increment syntax, dict literals, and triple-quoted strings/docstrings.
• Record current rejection stage/code only where directly evidenced.
• Clarify wording that could imply full support from token recognition alone.
• Keep related compatibility documents consistent only where a real contradiction exists.

Non-goals

• Implementing any of these constructs.
• Adding new diagnostic behavior.
• Changing the pinned oracle or release-gate corpus.

Acceptance criteria

• Phase-1 unsupported constructs are explicitly covered by the support matrix.
• Lexing, parsing, semantic, and emission support are not conflated.
• No production behavior changes are included.
• Existing tests remain green.

Architect reviews contract accuracy; QA checks wording against current observable behavior.

[Teakowa]

Closing #84. Deferred-surface alignment landed in c57dbdb (+15 lines in docs/opy/support-matrix.md), naming backslash line continuations, ++/-- postfix, dict literals, and triple-quoted docstrings with their observed rejection stages/codes/fixture locations; wording correction for the -- parenthetical landed in 096891f. QA verified every bullet against observed behavior at f5fe337 and the pinned-9.7.10 oracle snapshots (reassessment a609062): all stage/code/location claims accurate. Docs-only change; no behavior impact; CI green on 096891f (run 31731754585).