Deck reader: case-insensitive node names and .equiv pseudonyms (documented) #156

Problem

User's Guide §1.1: "Everything is case INsensitive". §1.3: "Uppercase is converted to lower case". The guide's own §1.2 deck defines N3 and later writes .equiv nin n3. Our reader matches node names case-sensitively, a recorded choice in docs/fasthenry-compat.md ("Node/element names case-sensitive"), so that deck fails with unknown node 'n3'. 2 of the 19 runnable example decks stop here.

Measured (self-authored decks):

1. Names are case-insensitive everywhere: node definitions, segment endpoints, .external, .equiv, and in-plane node names. Output names are lowercased. Defining n1 and then N1 is a duplicate-definition error.
2. There are no forward references. A segment endpoint, .external or .equiv naming a node defined on a later line is an error. This matches ours.
3. .equiv pseudonyms (documented §1.3.7: "If any of the node names are not previously defined, then they become pseudonyms for those nodes in the list which are defined"):
   • .equiv nalias n3 lets nalias be used in .external and as a later segment endpoint;
   • an undefined name in the middle of the list works;
   • all names undefined is an error ("No real nodes in equiv statement");
   • defining a node after it became a pseudonym is a duplicate error.
4. .equiv chains transitively (ours already does).
5. .equiv n2 n2 is only a warning in FastHenry. Ours errors.

Expected

• All modes (documented): fold node names to lowercase for matching, so N1/n1 becomes a duplicate-name error, never two nodes. Output keeps the deck's first spelling or lowercases it; pick one and document it. Implement .equiv pseudonym creation for not-yet-defined names, with the "no defined node in .equiv" error when none exist. Keep the no-forward-reference errors.
• --fasthenry-compat only: .equiv x x becomes a warning. Native mode: error, as now.
• Note that this reverses the compat-table decision. A native deck that relied on N1 ≠ n1 now gets an explicit duplicate error rather than a silent reinterpretation.

Acceptance criteria

• Mixed-case references resolve in every position (segment ends, .external, .equiv, in-plane nodes).
• Case-only duplicates are an error.
• Pseudonym tests: alias first, alias last, alias in the middle, all-undefined error, define-after-alias error.
• Compat: .equiv x x warns.
• Compat-table "case-sensitive" row reversed, with rationale.

Clean-room provenance

Specified from the public FastHenry User's Guide / nonuniform ground-plane manual and from black-box runs of a locally built FastHenry on self-authored decks (2026-10-05, research for #74). No FastHenry source or distributed example deck was consulted or quoted; implement from this spec and the public docs only (CONTRIBUTING.md). Found by tools/fasthenry_compare.py over the FastHenry example corpus (#74).

Part of #76.

Implementation Guidance

Curation refresh, 2026-10-06: implementation is already proposed in PR #164. Review that PR against this scope rather than starting a second implementation. Its reported test results are not independently re-run by this curation pass.

Centralize node-name normalization in the name registry so declarations and references share the same rule. Pseudonyms should point to existing node slots without creating geometry. Choose a defined node from anywhere in an .equiv list before processing undefined names; retain transitive alias resolution and slot compaction. A compat self-equivalence warning must not prevent later entries in the same list from being joined. Include the named nodes in contact equiv_rect and contact connection when checking in-plane name handling. Document the chosen output spelling; explicit port labels and this reader's extension group= names are outside this node-name change.

Affected Files

• fasterhenry-cli/src/inp.rs — name registry, .equiv parsing, node reference/definition paths, parser documentation and unit tests.
• fasterhenry-cli/src/cli.rs — keep compatibility help consistent with the self-equivalence warning behavior.
• docs/fasthenry-compat.md — revise node-name and .equiv rows and explain the documented behavior replacing the previous decision.
• CHANGELOG.md — record the observable parser compatibility changes.

Test Plan

• Parser tests compare mixed-case and lowercase self-authored decks in native and compat modes, including segment endpoints, .external, .equiv, ordinary in-plane nodes and named contact-area nodes.
• Check ordinary/in-plane case-only collisions and define-after-pseudonym collisions produce line-numbered errors.
• Exercise alias first/last/middle, mixed-case aliases, all-undefined .equiv, and transitive chains; verify aliases add no extra geometry and yield the same solved deck as direct node references.
• Preserve unknown-node errors for segment and port forward references; .equiv pseudonyms must not permit an all-undefined list.
• Native self-equivalence still errors; compat emits a warning and continues joining later names in the list, including names already joined transitively.
• Verify default port-label spelling matches the documented choice and explicit labels retain their spelling.
• Run cargo test -p fasterhenry-cli, cargo fmt --all -- --check, and cargo clippy --workspace --all-targets -- -D warnings using the repository's isolated Cargo target workflow. Use only self-authored fixtures per CONTRIBUTING.md.

Verified corrections

• 2026-10-06, verified against origin/main @ e5d924abb67d149f1f3a066678078c36af2c3e7e (source inspection of Names::{define,lookup}, Parser::apply_equiv, apply_external, apply_node, and apply_plane_corner_form in fasterhenry-cli/src/inp.rs): registry keys currently use exact strings; .equiv looks up every name and rejects equal resolved slots. Ordinary and corner-form in-plane declarations both reach Names::define. These paths establish the parser locations above; they are not a fresh measurement of FastHenry behavior.
• 2026-10-06, verified via GitHub REST (GET /repos/2AMLogic/fasterhenry/pulls/164 and /pulls/164/files): PR Deck reader: case-insensitive node names and .equiv pseudonyms #164 is open at head 2b47666f163c387ca5ffdd8478fbb27f70d7278c, references this issue, and modifies the four files above. All four exist on the fetched build base (git ls-tree -r origin/main --name-only). Duplicate checking reported this related PR; the open backlog has no eligible sibling micro-issue to consolidate.