/**
 * Targeted prune of content-free BRAIN observations (T12073).
 *
 * ## Why (measured, 2026-08-06)
 *
 * Of 6,985 observations in this project's BRAIN:
 *
 * | count | share | shape                                          |
 * |-------|-------|------------------------------------------------|
 * | 2,012 | 29%   | narrative contains the literal `status: undefined` |
 * | 2,035 | 29%   | auto-hook `Task start:` / `Task complete:` stubs |
 * | 2,064 | 30%   | narrative under 60 characters                   |
 * |   481 | 6.9%  | narrative over 800 characters — i.e. substantive |
 *
 * The `status: undefined` rows are pure artefact: `PostToolUse` was dispatched
 * with a field name the payload does not declare, so `handleToolComplete`
 * interpolated `undefined` into every completion record. That defect is fixed
 * (T12071) and can no longer produce new rows — but the existing ones remain,
 * and they are not merely inert. FTS5's BM25 normalises for document length,
 * so a 44-character record OUTRANKS a 4,000-character one for any term they
 * share. The junk actively buries the knowledge.
 *
 * ## Safety
 *
 * This module is deliberately NOT the older `purgeBrainNoise`, which is a
 * one-shot script hardcoded to a historical state: it deletes every learning,
 * every decision but one specific id, and logs to stdout. Running it today
 * would destroy 127 learnings and 127 decisions.
 *
 * Here, instead:
 *
 *   - **Dry-run is the default.** Deleting requires an explicit `apply`.
 *   - Only OBSERVATIONS are considered. Decisions, patterns and learnings are
 *     never touched.
 *   - A row is a candidate only if it matches a named, narrow rule AND its
 *     narrative is under {@link MAX_STUB_NARRATIVE} characters, so a long
 *     record that merely happens to quote one of these strings survives.
 *   - Rows carrying `verified = 1` are always preserved.
 *   - The result reports per-rule counts and a sample, so the caller can see
 *     what would go before anything does.
 *
 * @task T12073
 */
import type { DatabaseSync } from 'node:sqlite';
/**
 * Longest narrative still eligible for pruning.
 *
 * A genuine write-up that happens to contain "status: undefined" (this
 * module's own documentation, for instance, or a post-mortem describing the
 * bug) is far longer than this and is therefore never a candidate.
 */
export declare const MAX_STUB_NARRATIVE = 200;
/** A named prune rule with its SQL predicate. */
export interface StubPruneRule {
    /** Stable identifier, reported in {@link StubPruneResult.byRule}. */
    readonly id: string;
    /** One-line explanation of what this rule removes and why it is safe. */
    readonly reason: string;
    /** SQL predicate over `brain_observations`, ANDed with the global guards. */
    readonly predicate: string;
}
/**
 * The prune rules, each narrow and independently justified.
 *
 * Every predicate is ANDed with `length(narrative) <= MAX_STUB_NARRATIVE` and
 * `verified IS NOT 1`, so no rule can reach a substantive or human-confirmed
 * record on its own.
 */
export declare const STUB_PRUNE_RULES: readonly StubPruneRule[];
/** One candidate row, for reporting. */
export interface StubPruneCandidate {
    readonly id: string;
    readonly title: string;
    readonly narrative: string;
    readonly rule: string;
}
/** Outcome of a prune run. */
export interface StubPruneResult {
    /** Whether rows were actually deleted (`false` = dry run). */
    readonly applied: boolean;
    /** Observation count before the run. */
    readonly before: number;
    /** Observation count after (equals `before` on a dry run). */
    readonly after: number;
    /** Number of rows matched (and deleted, when `applied`). */
    readonly matched: number;
    /** Per-rule match counts, keyed by {@link StubPruneRule.id}. */
    readonly byRule: Record<string, number>;
    /** Up to 5 example rows, so a dry run shows what would go. */
    readonly sample: readonly StubPruneCandidate[];
}
/**
 * Count, sample and optionally delete content-free observation stubs.
 *
 * @param nativeDb - open handle to the database holding `brain_observations`.
 * @param apply - when `true`, delete the matched rows; otherwise report only.
 * @returns counts, per-rule breakdown and a sample of matched rows.
 *
 * @example
 * ```ts
 * const preview = pruneObservationStubs(db, false);
 * console.log(`${preview.matched} of ${preview.before} observations are stubs`);
 * if (preview.matched > 0) pruneObservationStubs(db, true);
 * ```
 *
 * @task T12073
 */
export declare function pruneObservationStubs(nativeDb: DatabaseSync, apply: boolean): StubPruneResult;
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