bazel/sqlite3: add shared-lib wrapper for mattn/go-sqlite3 consumers

Introduce the building blocks required to redirect github.com/mattn/go-sqlite3
to the agent's own libsqlite3, without yet enabling the migration:

- deps/sqlite3.BUILD.bazel: cherry-pick the feature defines that the binding
  applies in its bundled-amalgamation build (sqlite3.go:13-23) so the shared
  libsqlite3 is feature-equivalent. Add :libsqlite3_headers, :_libsqlite3_shared
  (cc_import of the cc_shared_library output), and :libsqlite3_dynamic, the
  cdeps-consumable wrapper. Pattern mirrors //rtloader:rtloader_dynamic.

- bazel/rules/go_sqlite3/go_sqlite3_library.bzl: a go_library wrapper that
  enables cgo and injects @sqlite3//:libsqlite3_dynamic as a cdep, plus a
  TODO for the install-time rpath fix-up that will be needed once the agent
  binary is built with Bazel.

- bazel/rules/go_sqlite3/BUILD.bazel: alias forwarding to
  @sqlite3//:libsqlite3_dynamic. @sqlite3 isn't visible from the bzlmod
  context of the gazelle-generated go-sqlite3 repo; the @@//... label
  resolves regardless and insulates the macro from canonical-name churn.

No behavior change yet: these targets are inert until the gazelle override
that emits go_sqlite3_library lands in a follow-up commit.

Author: chouquette

bazel/rules/go_sqlite3/BUILD.bazel

@@ -0,0 +1,9 @@
+# Indirection so go_sqlite3_library can reference libsqlite3_dynamic via a
+# main-module label. @sqlite3 isn't visible from inside the bzlmod context of
+# the gazelle-generated github.com/mattn/go-sqlite3 repo; @@//... always
+# resolves and insulates the macro from canonical-name churn.
+alias(
+    name = "libsqlite3_dynamic",
+    actual = "@sqlite3//:libsqlite3_dynamic",
+    visibility = ["//visibility:public"],
+)

bazel/rules/go_sqlite3/go_sqlite3_library.bzl

@@ -0,0 +1,30 @@
+"""go_library wrapper that links github.com/mattn/go-sqlite3 against //deps:sqlite3."""
+
+load("@rules_go//go:def.bzl", _go_library = "go_library")
+
+def go_sqlite3_library(**kwargs):
+    """Wraps go_library so the Gazelle-generated rule for mattn/go-sqlite3
+    enables cgo and pulls in @sqlite3//:libsqlite3_dynamic as a cdep.
+
+    Wired in via gazelle:map_kind on github.com/mattn/go-sqlite3 (see
+    deps/go.MODULE.bazel). The libsqlite3 Go build tag is enabled globally
+    in .bazelrc, so sqlite3_libsqlite3.go defines USE_LIBSQLITE3 and the
+    bundled amalgamation in sqlite3-binding.c is a no-op TU.
+
+    TODO(agent-build): when the agent binary is built with Bazel, its rpath
+    will point into bazel-bin/_solib_local/... and won't resolve at install
+    time. Apply the same packaging path used for cpython: pull
+    @sqlite3//:sqlite3_pkg into the binary's packaging deps and run the
+    bazel/rules/rewrite_rpath rule post-link to retarget to the install-tree
+    libsqlite3.so location.
+
+    Args:
+      **kwargs: forwarded to go_library. cdeps is extended (not replaced) so
+        Gazelle-emitted entries are preserved.
+    """
+    kwargs["cgo"] = True
+    cdeps = kwargs.pop("cdeps", [])
+    label = "@@//bazel/rules/go_sqlite3:libsqlite3_dynamic"
+    if label not in cdeps:
+        cdeps = cdeps + [label]
+    _go_library(cdeps = cdeps, **kwargs)

deps/sqlite3.BUILD.bazel

@@ -1,5 +1,5 @@
 load("@@//bazel/rules/dd_packaging:dd_cc_packaged.bzl", "dd_cc_packaged")
-load("@rules_cc//cc:defs.bzl", "cc_library", "cc_shared_library")
+load("@rules_cc//cc:defs.bzl", "cc_import", "cc_library", "cc_shared_library")
 load("@rules_license//rules:license.bzl", "license")
 
 package(
@@ -26,10 +26,20 @@ cc_library(
     srcs = ["sqlite3.c"],
     hdrs = _SQLITE3_PUBLIC_HEADERS,
     includes = ["."],
+    # SQLITE_* defines mirror mattn/go-sqlite3's bundled-amalgamation build
+    # (sqlite3.go:13-23) so this shared library is feature-equivalent to the
+    # binding's default flavor.
     copts = [
         "-Wall",
+        "-DSQLITE_DEFAULT_WAL_SYNCHRONOUS=1",
+        "-DSQLITE_ENABLE_FTS3",
+        "-DSQLITE_ENABLE_FTS3_PARENTHESIS",
         "-DSQLITE_ENABLE_MATH_FUNCTIONS",
+        "-DSQLITE_ENABLE_RTREE",
+        "-DSQLITE_ENABLE_UPDATE_DELETE_LIMIT",
+        "-DSQLITE_OMIT_DEPRECATED",
         "-DSQLITE_THREADSAFE=1",
+        "-DSQLITE_TRACE_SIZE_LIMIT=15",
         "-O2",
     ],
     linkstatic = True,
@@ -42,6 +52,22 @@ cc_shared_library(
     visibility = ["//visibility:public"],
 )
 
+cc_import(
+    name = "_libsqlite3_shared",
+    shared_library = ":sqlite3",
+)
+
+# This target is meant to be used as a cdeps for go code that relies on sqlite3
+# More specifically, it's intended to avoid rebuilding the sqlite3 amalgamation
+# in github.com/mattn/go-sqlite3
+cc_library(
+    name = "libsqlite3_dynamic",
+    hdrs = _SQLITE3_PUBLIC_HEADERS,
+    includes = ["."],
+    visibility = ["//visibility:public"],
+    deps = [":_libsqlite3_shared"],
+)
+
 dd_cc_packaged(
     name = "sqlite3_pkg",
     input = ":sqlite3",