neo4j(v2): drop bare labels + rename rel types to TS_* in the CanNode contract (graph schema 2.0.0)

[rahlk]

PROBLEM

After stage 1 (dual labels, graph schema 1.1.0), the graph still carries the bare specific labels and unprefixed relationship types. The breaking completion must land exactly once, inside the in-flight v2/CanNode contract (the fix/issue-46-bolt-symbol-labels line), so consumers absorb a single 2.0.0 instead of two consecutive majors.

SCOPE BOUNDARY

This is a change to the v2 contract line, not main's v1 emitter. CanNode stays unprefixed by design: it merges on can:// ids, which embed the language, so cross-language collision is impossible at the merge layer — do not prefix it. analysis.json untouched.

GOALS

1. Drop the bare specific labels: nodes carry only the TS* twin (plus CanNode).
2. Rename every relationship type to TS_* (TS_HAS_MODULE, TS_DECLARES, TS_HAS_METHOD, TS_HAS_FIELD, TS_HAS_BODY_NODE, TS_RESOLVES_TO, TS_CALLS, TS_CFG_NEXT, TS_CDG, TS_DDG, TS_SUMMARY, TS_PARAM_IN, TS_PARAM_OUT, TS_EXTENDS, TS_IMPLEMENTS).
3. SCHEMA_VERSION → 2.0.0; conformance test asserts no undeclared (and no bare) label or rel type is emitted.
4. Regenerate schema.neo4j.json; release notes flag the breaking rename with the one-line migration (re-analyze; update queries Callable→TSCallable, CALLS→TS_CALLS).

CAVEATS AND KNOWN RISKS

• The v2 line also changes the merge key (Symbol{signature} → CanNode{id}); sequencing inside that branch matters — land the prefix after the CanNode merge-label switch so the conformance test churns once.
• python-sdk's TS Neo4j backend breaks on this release by design; the SDK child must merge and release before the pin moves (lockstep rule in the epic).

DEFINITION OF DONE

• On the fixture app: zero nodes match any bare specific label; zero rels match any unprefixed type; CanNode count unchanged from pre-change v2 output.
• Conformance test green; schema_version = "2.0.0" stamped.

Absorbs #9 and #10.

Part of #64