Preserve csvq expressions in custom rules

When a project has custom [experimental.inspect.rules] using normal csvq SELECT expressions (for example SELECT COALESCE(name, '-') FROM ... or other functions/operators), the Go implementation passes r.Query directly to the csvq driver and scans the first column, but this parser only accepts an aggregate call or a bare column reference. Those valid custom rules now render a parser error in the STATUS cell instead of evaluating to pass/fail, so existing report rules outside the built-in subset regress.

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The parity description is accurate: Go hands r.Query straight to the real csvq driver (apps/cli-go/internal/inspect/report.go), so a custom rule using full csvq syntax — COALESCE, CASE, joins, subqueries, etc. — evaluates to a real pass/fail there. This evaluator implements only a bounded subset (SELECT <agg|bare-column> FROM \csv` [WHERE ...]), so an out-of-subset custom rule surfaces a parser-error STATUS cell instead of a result. The 7 built-in default rules (templates/rules.toml`) are all inside the supported grammar and test-covered, so there is no regression for them; custom rules outside the subset do diverge from Go.

This is a deliberate, documented limitation (see the header of report.csvq.ts): there is no JS/TS port of mithrandie/csvq, and neither DuckDB nor alasql accepts csvq's dialect, so closing the gap fully means reimplementing the csvq expression dialect in TS — a large piece of work, not a quick follow-up. Flagging this as a scope decision for a maintainer rather than silently absorbing the divergence or pulling a full csvq reimplementation into this PR; leaving the thread open. Options:

• (a) accept the bounded subset as the documented limit and track full csvq support as a follow-up issue;
• (b) detect out-of-subset queries and emit a clearer "unsupported csvq expression" STATUS rather than a raw parser error;
• (c) treat full custom-rule parity as in-scope here (large reimplementation; own PR).

Stream COPY output instead of buffering it

For databases with many tables/indexes, report CSVs such as table or index stats can become large, but this accumulates every COPY chunk in memory, concatenates the full buffer, and the caller then keeps those bytes for rule evaluation. The Go implementation streams CopyTo directly into the output file, so this port can exhaust the Bun process heap or stall on a large report where the Go CLI would complete with bounded memory.

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You're right that Go streams CopyTo straight into the file (internal/inspect/report.go:64-77) and re-reads the CSVs from disk for the rules check (sql.Open("csvq", outDir), report.go:97), so its peak memory is bounded, whereas this port buffers each COPY via Buffer.concat and pins the CSVs in an in-memory map for rule evaluation.

This is purely a resource/robustness difference, not an output one — the CSV bytes, the rules table, and the exit code are byte-identical to Go on every observable dimension (the server serializes the CSV; the TS side never touches the values), and the report runs a fixed set of catalog-stat queries rather than streaming row data, so the OOM risk is confined to pathologically large databases. Matching Go's streaming means reshaping the copyToCsv driver seam (take an output path / return a write sink) and switching the rule evaluator to read CSVs back from disk — and that seam has already changed a couple of times this review cycle. I'd rather land the byte-identical behavior now and do the streaming rework as a focused follow-up with its own tests; tracking it rather than folding it in here. Leaving this thread open for that follow-up.

Avoid opening a second connection for COPY

When the target role/database has only one free connection slot (for example a CONNECTION LIMIT 1 role or a saturated max_connections), connect already holds the probed PgClient, and the first copyToCsv then dials this additional pg.Client. The Go report path reuses the single conn.PgConn() returned by ConnectByConfig for CopyTo, so it can succeed in that environment while this port fails before writing the report. Please run COPY on the existing/raw connection or release the probe connection before opening the COPY client.

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Reject invalid inspect config instead of defaulting

When config.toml has an invalid inspect section with no valid rules key, such as [experimental.inspect] ruless = [...] or inspect = "bad", this treats the rules as absent and runs the default checks. Go loads the whole config with UnmarshalExact into Experimental.Inspect, so unknown fields or the wrong shape under experimental.inspect abort before any report queries; silently defaulting hides misspelled custom rules. Please validate the inspect section's shape and keys before returning [].

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Preserve CSV nulls when evaluating rules

When a report CSV contains an unquoted empty field from a SQL NULL (for example db_stats.index_hit_rate can be NULL when the hit-rate denominator is zero), csvq imports that as NULL, but this parser collapses it to the same "" value as a quoted empty string. The default cache-hit rule can then string-compare "" < 0.94 and report a failure where Go's csvq evaluates NULL < 0.94 as unknown and excludes the row; custom rules using IS NULL, COUNT(col), or aggregates over nullable columns drift for the same reason. Please track whether a field was quoted/unquoted and model unquoted empty fields as NULL.

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Apply matching remote inspect rules

When the linked project matches a [remotes.<name>] block that defines its own [remotes.<name>.experimental.inspect.rules], Go resolves the project ref before LoadConfig and merges that remote block before printSummary, but this reader only looks at the top-level experimental.inspect table. Those remote-specific report rules are ignored and the command falls back to the top-level/default rules for the linked project, so multi-environment configs validate the wrong policy. Please merge the matching remote config or defer rule loading until after the linked ref is known.

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