Merge the two workflow analyzers into one in NodePilot.Core

[Sev7eNup]

Problem

analyze_workflow existed twice — WorkflowReviewAnalyzer (Core, behind the AI chat) and WorkflowAnalyzer (Mcp/Analysis, behind the MCP tool). Both mirrored the canvas linter independently, with no parity test between them, and they had already drifted:

• cycle was an error on one side and a warning on the other, though the engine has no inDegree fallback and a cyclic graph Fails outright;
• the chat copy flagged missing-target-machine on runScript/waitForCondition, which the Localhost bypass makes perfectly valid — it told authors to "fix" a correct workflow;
• the chat copy did not know unresolvable {{...}} references at all, so a log message reading {{gibtsnicht.output}} analysed as ok with no findings and then failed on the first run.

Change

The MCP implementation was the superset and moves to NodePilot.Core.WorkflowDefinitions, keeping the structural pre-check and the empty-workflow case from the Core copy. Both surfaces now call it, so their findings can no longer disagree. Mcp/Analysis/VariableResolver moves along as WorkflowDataBusAnalyzer — the rename avoids a collision with the engine's runtime VariableResolver, which Core is visible to.

Two behaviour notes:

• the analyzer no longer reports unknown-activity-type of its own, because the structural pre-check already rejects it and names the node index and the offending type;
• ok now means "no error-severity finding" on both surfaces, with warnings still counted in count/findings.

WorkflowAnalyzerFrontendParityTests moves to Engine.Tests, where Core-level guards live, and becomes the single mirror guard against workflowLint.ts. A roadmap entry under E records the direction that was not taken — routing the chat through nodepilot-mcp — and why: one DPAPI session versus per-request ClaimsPrincipal, loopback HTTP per call, and ~90 write tools the chat deliberately lacks.

Second commit: a guard that the move broke

TemplateGrammarParityTests locates the databus analyzer by path and still read src/NodePilot.Mcp/Analysis/VariableResolver.cs. It threw FileNotFoundException instead of comparing anything. Fixed to the new path, with the file's existence now asserted explicitly so the failure names the path to update rather than surfacing as an IO stack trace.

Tests

Full solution builds. Ran:

project	result
NodePilot.Engine.Tests	1873 passed (was 1838 — the parity + analyzer tests landed here)
NodePilot.Mcp.Tests	165 passed (was 181 — 16 moved to Engine.Tests)
NodePilot.Ai.Tests	497 passed