docs/program-format: document TIMED sunrise/sunset offset encoding

New section explaining the hour-byte overload (25 = sunrise-relative,
26 = sunset-relative, with the minute byte read as sbyte for the
offset). Python example showing TimeKind classification +
format_time() output. Removes the corresponding line from the
"what we don't yet know" list.

src/content/docs/reference/program-format.mdx

@@ -152,6 +152,40 @@ Decoded as a file record:
 So: "TIMED program firing at 07:15 on weekdays, doing command 0x44 with
 par=3 and pr2=256, gated by the condition pair 0x8d09 / 0x9b09."
 
+## TIMED programs: absolute time vs sunrise/sunset offset
+
+The `hour` byte at offset 12 is **overloaded** as a one-of-three
+discriminator:
+
+| `hour` byte | Meaning |
+|-------------|---------|
+| 0 – 23 | Absolute wall-clock time. `minute` is unsigned 0-59. |
+| **25** | Sunrise-relative. `minute` is read as a **signed** byte. |
+| **26** | Sunset-relative. `minute` is read as a **signed** byte. |
+
+For the sunrise/sunset forms, the signed `minute` byte is the offset
+in minutes: positive = *after*, negative = *before*, zero = *at*.
+
+```python
+from omni_pca.programs import Program, ProgramType, TimeKind
+
+p = Program(prog_type=int(ProgramType.TIMED), hour=26, minute=246, days=0x40)
+assert p.time_kind == TimeKind.SUNSET
+assert p.time_offset_minutes == -10              # 246 as sbyte == -10
+assert p.format_time() == "10 min before sunset"
+```
+
+The decoder hides the sbyte trick behind a `time_kind` property and a
+`time_offset_minutes` view; the original `hour` / `minute` bytes are
+still on the dataclass for round-trip fidelity. `format_time()`
+renders a friendly label so HA entity callers get
+`"30 min after sunrise"` rather than `(25, 30)`.
+
+Source: `frmPopUpEditTime.cs:186-217` (decode) and `:241-263` (encode)
+in the decompiled PC Access form. The Owner's Manual ("±0-120 minutes")
+is a UI-level constraint; the wire encoding supports the full
+sbyte range (-128..127).
+
 ## Quirk: the `EVENT` Mon/Day swap
 
 For `EVENT`-typed programs on disk only, bytes 9 and 10 are stored in the
@@ -239,11 +273,6 @@ pass. So is the multi-record clausal encoding hinted at by the
   records for the Omni Pro II. Other models may use the 12-byte form.
   Locating where the panel advertises the flag (and which non-OPII
   models clear it) is its own follow-up.
-- **TIMED time-of-day encoding.** Some TIMED programs in the live
-  fixture have `hour > 23` or `minute > 59`, suggesting bytes 12/13
-  also encode sunrise/sunset-relative offsets (Owner's Manual:
-  ±0-120 minutes). The flag distinguishing absolute time from
-  relative offset has not been isolated.
 
 ## Python usage