[psteinroe]

Bring back parameter-name inlay hints, and make hover show what a name actually resolves to. Both are built on a new opt-in API on the catalog resolver that returns resolved references, not just errors.

Resolved references (pgls_catalog)

resolve can now also return what the names of a statement resolve to. This is enabled with ResolveParams::collect_references and returned in Resolution::references:

• Function { function, arguments }: the overload a call resolves to via select_function, and which parameter each argument goes to.
• Column { source, column }: source is a catalog relation, a CTE or a subquery alias. The column is recorded under its source's own name, even when an alias renames it. CTE and subquery columns carry their inferred type.
• Relation { relation }: catalog relations in FROM and the targets of INSERT, UPDATE, DELETE and COPY.

Each reference has a location and span. A reference is only recorded when a name resolves to exactly one object. The linter passes false, so nothing is collected or allocated on its path, and a test checks that findings are identical either way. Explicit VARIADIC calls now go through overload resolution too, but are never reported. The Postgres regression suite passes, so typecheck findings are unchanged.

Inlay hints

A name: hint before positional function arguments when the call resolves to exactly one function:

select make_point(1, 2 + 3);      -- make_point(x: 1, y: 2 + 3)
select make_point(1, y => 2);     -- make_point(x: 1, y => 2)
select sum_all(1, 2, 3);          -- sum_all(base: 1, nums: 2, 3)

No hints for named arguments, unnamed parameters, arguments already named like the parameter, ambiguous or unknown calls, or SQL-syntax calls like EXTRACT. Adds the new pgls_inlay_hints crate, pull_inlay_hints in the workspace, and inlayHintProvider with a textDocument/inlayHint handler in the language server.

Hover

Hover resolves the innermost statement at the cursor with the file's DDL applied:

• Functions: only the overload the call resolves to, instead of every overload with that name.
• Columns: the column of the relation it actually comes from, through aliases and joins.
• Relations: the table the search path picks.
• CTE and subquery columns: a small new hover with their inferred type.

It falls back to today's name-based lookup when there is no unique reference. Hover now also works inside SQL function bodies. All existing hover snapshots are unchanged.

create function pick(i integer) returns integer ...;
create function pick(t text) returns text ...;
select pick(1);   -- hover: only `public.pick(i integer) → integer`

Risks and gaps

• Hover and inlay hints walk the file up to the cursor or visible range and apply its DDL. This is shared in the new walk_statements helper. It's fine for typical files, but adds cost on very long ones.
• walk_statements follows dbmate/goose migration sections like the analyser does. Each section gets its own session, and a down section sees the catalog after the up sections before it, without carrying its own DDL into the next section. Hover and inlay hints still work in down sections skipped with lintDown: false, because those sections are only excluded from linting.
• No column references yet for INSERT column lists, UPDATE SET targets, excluded/old/new, NATURAL joins, or columns of functions in FROM. Hovering a table alias (u in u.name) still uses the name lookup.
• CALL proc(...) gets no inlay hints, because the resolver doesn't handle CallStmt.

Fixes #130