fix(engine): an alphabetical tie between same-number notes gates a note nobody ordered #233

Problem

palee adopt --auto-chain orders notes inside a directory by numeric prefix, then phase rank, then alphabetically. When two notes carry the same prefix — m/02-a.md and m/02-b.md, or lab-a.md and lab-b.md — the tree declines to choose between them and the filename collation does. That edge was written with depends_on_source: numbered, and numbered gates.

Measured on the current stack tip: a vault of m/02-a.md + m/02-b.md adopts one edge, reported as 1 numbered, and palee plan --json offers only m/02-a.md. Because no v0.5.x command raised topic_mastery before #228, that lock was permanent.

This is the defect PAL-205 contains for enumeration order — a note hidden behind a position nobody asserted — one level lower in the same planner. The CLI already admits it: the warning says "the order between them is alphabetical".

Approach

Split the label from the consequence. A tie-derived edge is written as depends_on_source: tie and tie joins toc in the advisory set, so:

• the edge still ranks the note and still takes part in cycle detection;
• it never holds a note off the ready list;
• an absent or unrecognized label still gates — fail-closed is untouched, advisory status is granted only by exact name.

numberedEdgeCount keeps counting tie edges, because that number answers the honest-refusal question ("did any planner produce an order?"), not the gating question.

Acceptance criteria

• A same-number pair writes its edge with depends_on_source: tie, not numbered.
• palee plan offers both notes while the first is unmastered.
• The dry-run and commit reports name the tie separately: 1 edge(s) written: 0 numbered, 0 toc, 1 tie (advisory).
• tie round-trips through the loader and through an old build's parser without being rejected.
• A vault whose only edges are ties is not reported as "no chainable order signal".
• Unrecognized and absent labels still gate.
• Each guard ships with a test that fails when its deciding predicate is reverted.

Environment

Repo Kuldeep2822k/cli, branch fix/palee-tie-advisory stacked on test/pal205-gate-hygiene (#226) → fix/palee-gating-policy (#223) → feat/73-tier-sources (#215). Node 24, @kuldeep2822k/palee 0.5.2.