fix(sl): correct reserved-word/week-grain SQL and classify sl_query errors (#340)

Reserved-word columns (like, default, ...) referenced as source.col were
quoted with postgres double quotes even on BigQuery/MySQL, where a
double-quoted token is a string literal, not an identifier -- the
"Unexpected string literal" semantic-layer errors. quote_reserved_identifiers
now uses the identifier quote char of the dialect it will be parsed in
(backtick for BigQuery/MySQL), threaded through the planner and generator
parse sites; week_<weekday> granularity now emits WEEK(<weekday>) on BigQuery
instead of the invalid WEEK_MONDAY.

On the telemetry side, warehouse rejections from the sl_query execution path
are classified as expected (KtxQueryError) via a new shared markExpected()
helper, so routine agent/warehouse query failures stop reaching PostHog Error
Tracking as ktx faults; the sql_execution catch is refactored onto the same
helper. The daemon-compile boundary is deliberately left unclassified here so
genuine daemon crashes stay visible.

python/ktx-sl/semantic_layer/planner.py

@@ -694,7 +694,8 @@ class QueryPlanner:
                 all_dep_names.add(dep_name)
                 named.add(dep_name)
             tree = sqlglot.parse_one(
-                f"SELECT {quote_reserved_identifiers(expr)}", dialect=self.dialect
+                f"SELECT {quote_reserved_identifiers(expr, self.dialect)}",
+                dialect=self.dialect,
             )
 
             def _replace(node):
@@ -738,7 +739,8 @@ class QueryPlanner:
         """Reject expressions with nested aggregate functions (e.g., avg(sum(x)))."""
         try:
             tree = sqlglot.parse_one(
-                f"SELECT {quote_reserved_identifiers(expr)}", dialect=self.dialect
+                f"SELECT {quote_reserved_identifiers(expr, self.dialect)}",
+                dialect=self.dialect,
             )
             for agg_node in tree.find_all(exp.AggFunc):
                 # Check if this aggregate contains another aggregate inside