docs(architecture): add ARCH-14 — runtime test seams live in the TikoOptions override family

[tomas-samek]

Scope

Add the ARCH-14 entry proposed by the 0.4.0 tiko-architect gate run to the architecture invariants registry:

ARCH-14 — runtime test seams live in the TikoOptions override family. Test affordances that need a runtime hand-off (holding a fake to assert on it) are class-keyed, opt-in, container-owned-lifecycle builder methods on TikoOptions — the override(Class, ...) / replaceTransport(Class, Function) shape. No global test flags, no system properties, no ambient test mode.

Follow the registry's entry format: Statement, Rationale (codifies the resolved #414 compile-time-identity vs runtime-seam tension), Anchor (TikoOptions.replaceTransport javadoc + docs/superpowers/specs/2026-07-04-issue-414-transport-substitution-design.md), Violation-looks-like (a new test knob added as a system property / static flag / env variable instead of a TikoOptions builder method).

Files

• Modify: docs/architecture-invariants.md

Acceptance

• ARCH-14 entry present, matching the existing entries' structure.
• The registry intro's ID range ("ARCH-1 … ARCH-13") updated.

Predecessor

Proposed in the tiko-architect verdict for the v0.3.0..v0.4.0 delta (step-5 registry self-audit).