Merge branch 'worktree-agent-a63474e92b05425a5'

# Conflicts:
#	Cargo.lock
#	Cargo.toml

tickets/001-param-declarations.md

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+# 001 — Param declarations
+
+## Summary
+
+Implement the `ParamDeclaration` slice of the primary index: users can declare how a
+named parameter is derived from a log line (e.g. deriving a timestamp different from
+the ingestion timestamp, or a log level), and the engine stores/serves those
+declarations.
+
+## Scope
+
+- `IndexKey::ParamDeclaration { name }` and a matching `DataValue` variant for the
+  declaration body (a regex against the raw log text, plus how the capture maps to a
+  `MetricPrimitive` — reuse `RegexToMetricPrimitiveMatcher` / `MetricPrimitiveKind`
+  from `data_value.rs`, which already exist but are unused).
+- Engine message(s) to add/list/remove a param declaration.
+- Validate declared regexes at declaration time (reject invalid regex / unknown
+  primitive kind up front rather than failing per-log later).
+- No derivation/backfill against existing logs yet — that's
+  [002](002-metric-declarations.md) / [003](003-metric-bucket-derivation.md), since
+  metrics are what actually get indexed into buckets. This ticket is just the
+  declaration storage + validation.
+
+## Acceptance criteria
+
+- Declaring a param with a valid regex + capture group succeeds and is retrievable.
+- Declaring a param with an invalid regex or referencing a non-existent capture group
+  is rejected with a clear error, not silently stored.
+- Declarations sit in their own contiguous range of the BTreeMap
+  (`ParamDeclaration` between `LogParamSplit` and `ParamMetricSplit`), per the
+  `IndexKey` ordering in the README.
+
+## Depends on
+
+None — this is foundational.