fix: allow metadata probes on path lookups

[sabino]

What changed

• treat an unbound path-template endpoint as an empty parameterized lookup
• keep equality-bound path lookups issuing the same live HTTP request
• verify unbound probes make no outbound request
• add and package a real 0.3.1 to 0.3.2 PostgreSQL extension upgrade
• install every initial and upgrade SQL file from native archives

Why

Catalog and BI clients probe declared JSON fields with an unfiltered scan. A
path endpoint such as /items/{id} cannot make a valid request until id is
bound, and the previous hard error aborted the client field synchronization.
Returning an empty relation is conservative, preserves the declared tuple
descriptor, avoids a fake/default identifier, and performs no network work.

Validation

• cargo fmt --all -- --check
• Python and browser JavaScript syntax checks
• shell syntax checks
• native archive contract test
• native installer contract test
• YAML parsing
• cargo metadata --locked --no-deps
• full PostgreSQL 14 through 18 integration matrix
• full control-plane integration workflow