Adopt reviewed semantic-continuity wording

[GerhardBalz-Admin]

Summary

Reconciles current ESKA documentation with the initiative-level principle adopted in SKE PR #40:

Semantics must remain explicit through execution.

Changes

• updates the ESKA README to use the reviewed positive formulation as the primary principle;
• updates docs/semantic-continuity.md and its title while retaining “Execution must not sever semantics” as explanatory failure-mode shorthand;
• aligns docs/related-work.md with the reviewed invariant;
• aligns the active Pizza executable reference documentation;
• makes explicit that an Implementation Projection is optional: source-owned semantic artifacts may participate in execution directly, while projections—when used—must preserve relevant meaning and lineage.

Boundary

Documentation only. This PR does not:

• change ESKA vocabulary or ontology modules;
• modify runtime behavior or executable examples;
• modify/retag eska-v0.1.0 or eska-v0.2.0;
• rewrite historical PRs/issues/releases;
• add OntoJIT or other related work still awaiting separate review.

Downstream of: GerhardBalz/semantic-knowledge-engineering#40
Tracks completion of: GerhardBalz/semantic-knowledge-engineering#39