v2 chunk 3: bug fixes from real-draft triage + polish

Six independent fixes addressing the Anti-Communist Formations of LIS
real-draft test findings (chunk 2c). Four are bug fixes for issues
that destroyed user data or wasted API calls; two are polish quality
improvements revisited from the deferred list.

src/cmos/note_formatter.py — empty input guard (fix #1)
  Empty / whitespace-only input now short-circuits the API entirely
  and returns the input verbatim. Surfaced by note [66] in the
  Anti-Communist draft, where GPT-5 broke character on empty input
  and returned a conversational meta-reply ("Please paste the
  citation entry...") that then got substituted into the document.
  Whitespace preserved so cli.reformat_notes is byte-exact on empty
  notes. v2 only.

src/cmos/note_formatter.py — deprecated Latin guard (fix #2)
  New Python guard catches the full CMOS-18-deprecated Latin
  citation set (ibid, idem, id., op. cit., loc. cit.) and returns
  input verbatim before the API call. Rule 10 in the prompt also
  rewritten: explicitly says "return verbatim" instead of the old
  "return cleanest possible full-form note", which the model
  interpreted as "return empty when there's no information",
  silently destroying the marker. Surfaced by note [61] = "Ibid.".
  v2 only.

src/cmos/runtime_validator.py — shortened-form carve-out (fix #3)
  The "must contain italics" check is now skipped when the
  candidate looks like a CMOS shortened-form note (author last
  name, optional page, no italic content). Surfaced by ~30 of 107
  notes in the Anti-Communist draft that were correctly returned
  as shortened forms ("Rosen, 7.", "Mitchell, 197.") but rejected
  by the validator's strict italic check, firing the full retry
  budget on valid output (~60 wasted API calls per run). The
  carve-out is conservative: name-token regex + terminal period;
  doesn't match unstructured prose. Shared infrastructure — affects
  v1 and v2, no-op in v1's normal workflow because v1 outputs
  always have italics.

src/cmos/note_formatter.py — substantive prose pass-through (fix #4)
  Long discursive prose with no citation skeleton markers now
  short-circuits the API and returns the input verbatim. Surfaced
  by notes [8] (689 chars), [9] (893 chars), [75] (163 chars) in
  the Anti-Communist draft — substantive notes that the formatter
  was extracting a single citation from and silently discarding
  the surrounding commentary. CMOS 14.39 explicitly allows
  substantive notes; preserving them is the user's explicit policy
  ("preserve all free text as long as that does not break other
  formatting"). Detection: length > 150 chars AND no citation
  skeleton markers (parenthesized year, URL, vol./no./pp., DOI,
  terminal page or terminal year). Conservative — does not
  false-positive on legitimate first-occurrence notes. v2 only.

src/cmos/formatter.py + note_formatter.py — month/season preservation
  (polish #5)
  Both v1 rule 10 (journal article format) and v2 rule 5 (journal
  article note form) now explicitly instruct the model to preserve
  (Month YEAR) and (Season YEAR) parentheticals when the source
  provides them. Surfaced by entries in both Reading_Disrepair and
  Anti-Communist where (Spring, 1993) and August 1952 were silently
  collapsed to (1993) and 1952. Both forms are valid CMOS but
  month/season is more informative when the source has it. Affects
  v1 and v2 in mirror.

src/cmos/note_formatter.py — government documents rule 19 (polish #7)
  v2 now has an explicit rule mirroring v1's rule 27: government
  bodies, institutional reports, and similar standalone documents
  get italicized titles and book-form treatment, NOT quoted-article
  treatment. Includes the Anti-Communist Senate of California
  Tenth Report and a hypothetical GAO example. Implicit handling
  worked in chunk 2c, but explicit rule provides regression
  protection. v2 only.

Tests: +14 net new (across test_note_formatter.py, test_formatter.py,
test_runtime_validator.py). Total suite 150/150 (was 136 before this
chunk). All v1 tests still passing.

Path B status: formatter.py and runtime_validator.py edits cross
the v1/v2 boundary, but only by user-explicit approval per the
relevant fix discussions. The shared validator was always shared;
the v1 formatter rule 10 mirror is a small additive edit that
doesn't affect the v1 prompt's existing behavior on its existing
inputs.

tests/test_formatter.py

@@ -47,6 +47,22 @@ def test_system_prompt_mentions_italic_markers():
     assert "*" in SYSTEM_PROMPT and "italic" in SYSTEM_PROMPT.lower()
 
 
+def test_system_prompt_mentions_month_or_season_preservation():
+    """Polish fix #5: when the source provides month or season information
+    in a scholarly journal date, the formatter should preserve it in CMOS
+    form `(Month YEAR)` or `(Season YEAR)` rather than collapsing to
+    year-only. Surfaced by Reading_Disrepair (v1) and Anti-Communist (v2)
+    real-draft runs where dates like `(Spring, 1993)` and `August 1952`
+    were silently collapsed to `(1993)` and `1952`. Both forms are valid
+    CMOS but month/season is more informative when the source has it.
+    """
+    lower = SYSTEM_PROMPT.lower()
+    assert "month" in lower
+    assert "season" in lower
+    # And some indication of preservation, not collapse.
+    assert "preserve" in lower
+
+
 def test_build_user_message_contains_the_messy_input():
     msg = build_user_message("yu, charles. interior chinatown. 2020")
     assert "yu, charles. interior chinatown. 2020" in msg