fix(planner): apply deterministic proposal ordering (#1399)

[DevChiniwala]

Summary

Fixes #1399 by applying Decision 98 consistently to browser-local workflow
planning. Valid proposals are ordered shortest-chain-first, with ties broken
lexicographically by the ordered capability-id chain, before the five-proposal
limit is applied.

The TypeScript planner previously stopped after the sixth depth-first result.
That allowed an early longer chain to displace a shorter chain discovered
later. The Rust implementation already sorted the complete bounded result;
both implementations now consume one shared conformance fixture that captures
the mixed-length and tie-breaking case.

Governing Spec

• 1277-browser-local-workflow-composition
• 004-spec-alignment-gate

Project Item

• browserLocalPlan/build_chains: no stated preference among multiple valid-length proposals #1399

What Changed

• Contracts changed: Spec 1277 is amended to v0.2.0 with Decision 98's total
  ordering, post-ordering candidate limit, and no-preference rule.
• Runtime behavior changed: browserLocalPlan completes its bounded search,
  globally orders and deduplicates valid chains, then returns the first five.
  The 4,000-call and eight-node limits remain in force.
• Compatibility impact: response schemas and limits are unchanged; ambiguous
  TypeScript results may now appear in the approved deterministic order.
• ADR needed or linked: no new ADR; this implements Decision 98 recorded on
  browserLocalPlan/build_chains: no stated preference among multiple valid-length proposals #1399.

Validation

• Spec alignment checked
• Contract alignment checked
• Tests updated and passing
• Core coverage preserved
• Required validation gates passing

Validated locally:

• cargo +stable fmt --all -- --check
• cargo +stable test --locked -p traverse-embedder --lib browser_local_plan
  (24 passed)
• cargo +stable clippy --locked -p traverse-embedder --lib --tests -- -D warnings
• npm run build
• node --test tests/browserLocalPlan.test.mjs (28 passed)
• git diff --check

Notes

The full web package test command also requires the generated
packages/web/TraverseEmbedder/runtime/runtime.wasm, which is absent from a
fresh checkout. Its planner tests pass independently; CI remains authoritative
for the artifact-backed bundle suites.

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