fix(guidance): bind manufacturing claims to evidence

[neusse]

Problem and scope

PRs #362 and #363 connected the Claude package and made its claimed evidence executable, but the final #357 scope remained: manufacturing guidance still credited validate_for_manufacturing with checks it does not perform, treated partial exports as complete packages, duplicated conflicting vendor tables, and presented fixed trace/via/impedance geometry without the inputs required to justify it.

This is the focused guidance-only PR C. It closes the remaining #357 scope without depending on the conflicting #270 branch.

Design

• Bind the manufacturing preflight to the handler's observed contract: Edge.Cuts presence, footprint presence, configured minimum trace width, the no-tracks heuristic, and direct DRC evidence.
• Require fresh export destinations plus an artifact acceptance gate covering warnings, generated-file records, actual regular/non-empty files, Gerber/drill viewing, BOM/CPL inspection, and order-preview reconciliation.
• Treat an unavailable or contradictory required check as INCOMPLETE.
• Label estimate_cost as an indicative fixed-assumption heuristic rather than a quote.
• Replace duplicated JLCPCB prices, categories, limits, and template claims with a current-order-contract workflow that records source and retrieval date.
• Replace current/width, via, and controlled-impedance lookup tables with calculation inputs, stackup/field-solver evidence, project netclasses, and readback/DRC acceptance.
• Correct the Gerber reference: paste is not in the default layer selection, drill export is best-effort, and a directory listing is not artifact proof.
• Add a mechanical asset test that prevents the false claims and unsafe fixed tables from returning.

The wording is deliberately forward-compatible with #270: if a future response exposes a verified artifact manifest, the skill accepts that stronger evidence only for the postconditions it names. The viewer and order-preview gates remain.

Compatibility

Bundled Claude skills, references, and their asset tests change. MCP tools, schemas, response shapes, Rust export behavior, file formats, installer paths, and Codex behavior are unchanged. Because #270 edits Rust export modules while this PR edits bundled Markdown and asset_references.rs, there is no expected textual conflict.

Validation

Red baseline before the guidance rewrite:

• cargo test -p konnect --test asset_references manufacturing_guidance_is_contract_bound_and_fail_closed
• failed on the first missing current-contract marker (presence of at least one Edge.Cuts item)

After the rewrite:

• cargo test -p konnect --test asset_references: 12/12 passed
• cargo fmt --all -- --check: passed
• cargo clippy --workspace --locked --all-targets -- -D warnings: passed
• cargo test --workspace --locked --lib --tests: passed
• cargo test --workspace --locked --doc: passed

Real-KiCad GUI, installed-library, Java/Freerouting, and dedicated E2E cases remain ignored where their existing tests require those environments. This PR changes guidance only and does not claim those environment-dependent paths were exercised.

Risk and rollback

The workflow asks for more explicit evidence before manufacturing approval, which adds agent work to a full fabrication handoff. That work corresponds to checks the previous guidance already claimed had happened. The change can be reverted without data or API migration.

Closes #357.

[neusse]

Post-review follow-up #377 tracks the minor remaining ambiguity in the literal set_predefined_sizes example and extends the asset guard to cover that authority statement. It is guidance-only and does not block the manufacturing evidence corrections in this PR.