feat(text): add meta.* corpus-footprint layer and 4 language-aware primitives (v0.1.3)

Adds 12 new primitives across two waves of spec work this session.

meta.* layer (8 primitives) — corpus-snapshot footprint:
  total_messages, corpus_span_days, msg_per_day, active_days,
  activity_density, first_seen_ts, last_seen_ts, fingerprint_confidence.
  Motivated by two actors with identical message counts (53 each) producing
  indistinguishable profiles despite radically different presence shapes
  (0.3-day burst vs 47-day long tail).

Language-aware characterization primitives (4 primitives):
  stylometric.pos_ngram_signature — SimHash over POS bigram frequency vector;
    syntactic skeleton fingerprint that survives full vocabulary paraphrase.
  lexical.dialect_region — BCP-47 free_string (es-CL, es-AR, es-MX, …);
    designed for EYENET integration with INGEOTEC regional-spanish-models.
  lexical.evaluative_morphology_density — diminutive/augmentative/pejorative
    suffix density; stable per-author trait baked into language acquisition.
  lexical.optional_grammar_signature — SimHash over optional-grammar choice
    points (compound/simple past, subjunctive, leísmo, relative pronoun);
    high-reliability Spain vs LatAm discriminator.

Also fixes stale scratchpad.md references throughout (README.md is now the
authority), bumps behave-text to 0.1.3, and updates CHANGELOG.

BEHAVE-TEXT/tests/test_primitives.py

@@ -1,9 +1,9 @@
 # SPDX-License-Identifier: GPL-3.0-or-later
 """Registry coverage tests for BEHAVE-TEXT.
 
-Asserts that every primitive listed in scratchpad.md's tables has exactly one
+Asserts that every primitive listed in README.md's tables has exactly one
 entry in PRIMITIVE_REGISTRY. Drift-detector — failing this test means
-scratchpad.md and the registry have diverged.
+README.md and the registry have diverged.
 """
 
 from __future__ import annotations
@@ -13,9 +13,18 @@ from pathlib import Path
 
 from behave_text.spec import PRIMITIVE_REGISTRY, ValueKind
 
-# Primitive paths expected by scratchpad.md (hand-extracted; v0).
+# Primitive paths expected by README.md (hand-extracted; v0).
 EXPECTED_PRIMITIVES = {
-    # stylometric.* (motor analog — 8)
+    # meta.* (corpus-snapshot footprint — 8)
+    "meta.total_messages",
+    "meta.corpus_span_days",
+    "meta.msg_per_day",
+    "meta.active_days",
+    "meta.activity_density",
+    "meta.first_seen_ts",
+    "meta.last_seen_ts",
+    "meta.fingerprint_confidence",
+    # stylometric.* (motor analog — 13)
     "stylometric.punctuation_style",
     "stylometric.capitalization_habit",
     "stylometric.emoji_usage",
@@ -28,7 +37,8 @@ EXPECTED_PRIMITIVES = {
     "stylometric.function_word_distribution_top200",
     "stylometric.character_ngram_simhash",
     "stylometric.distinctive_vocabulary_signature",
-    # lexical.* (cognitive analog — 8)
+    "stylometric.pos_ngram_signature",
+    # lexical.* (cognitive analog — 11)
     "lexical.vocabulary_richness",
     "lexical.slang_density",
     "lexical.code_switching_rate",
@@ -37,6 +47,9 @@ EXPECTED_PRIMITIVES = {
     "lexical.sentence_complexity_class",
     "lexical.question_formation_style",
     "lexical.imperative_style",
+    "lexical.dialect_region",
+    "lexical.evaluative_morphology_density",
+    "lexical.optional_grammar_signature",
     # temporal_evolution.* (lifecycle/change-over-time — 1, added v0.2)
     "temporal_evolution.lifecycle_phase",
     # network.* (governance/role-shape — 2, added v0.3)