Revert "fix: improve metadata frame detection and update version to v0.12.1"

This reverts commit ad7b064b67.

docs/instantel_protocol_reference.md

@@ -103,7 +103,6 @@
 | 2026-04-11 | §5.1 | **CONFIRMED — SUB 0x06 (CHANNEL CONFIG READ) now confirmed as event storage range.** Two-step read, data offset = 0x24 (36 bytes). Token=0xFE at params[7]. Last 8 bytes of response: first stored event key (bytes −8:−4) and last stored event key (bytes −4:). Both equal `01110000` when device memory is empty. Used by Blastware to verify erase completion. |
 | 2026-04-11 | §7.11 (NEW) | **NEW — §7.11 Erase-All Protocol added.** Full wire sequence, SUB 0x06 storage range payload layout, post-erase key counter reset (resets to `0x01110000`). Confirmed from 4-11-26 MITM capture of live Blastware ACH session. |
 | 2026-04-11 | §14.6 | **RESOLVED — ACH Session Lifecycle is no longer "Future".** `bridges/ach_server.py` fully implements inbound ACH: POLL handshake, device info, event download. State tracked via `ach_state.json` (key-based, with `max_downloaded_key` for post-erase detection). `--clear-after-download` flag added for the standard delete-after-upload workflow. |
-| 2026-04-15 | §7.8.3 | **CORRECTED — Metadata frame detection must use multi-needle tuple, not `b"Project:"` alone.** Using only `b"Project:"` caused the metadata frame to be decoded as waveform ADC samples under certain conditions (serial number bytes `"BE11529\0"` appeared at sample ~929, followed by `0xFF 0xFF` fill). Root cause not fully characterised but `b"Project:"` alone is unreliable. Fix: check `_METADATA_FRAME_NEEDLES = (b"Project:", b"Client:", b"User Name:", b"Seis Loc:", b"Extended Notes", b"Geo: ")` against the full `rsp.data` bytes. `b"Geo: "` is the universal fallback — monitoring cannot operate without a configured geo threshold. Applied to both `_decode_a5_waveform` (client.py) and `read_bulk_waveform_stream` (protocol.py). |
 
 ---
 
@@ -824,9 +823,9 @@ Waveform: starts at byte 8 of db[7:]
 | Frame index | Contents |
 |---|---|
 | A5[0]  | Probe response: STRT record + first waveform chunk |
-| A5[fi] | Event-time metadata strings — position variable (fi==7 blast capture, fi==6 desk-thump; detect via `_METADATA_FRAME_NEEDLES`) |
-| A5[last] | Terminator frame (page_key=0x0000) — ignored |
-| All others | Waveform chunks |
+| A5[7]  | Event-time metadata strings only (no waveform data) |
+| A5[9]  | Terminator frame (page_key=0x0000) — ignored |
+| A5[1..6,8] | Waveform chunks |
 
 **Confirmed from 4-2-26 blast capture (total_samples=9306, pretrig=298, rate=1024 Hz):**
 
@@ -844,7 +843,7 @@ Total:     7633B  → 954 naive sample-sets, 948 alignment-corrected
 ```
 
 Only 948 of 9306 sample-sets captured (10%) — `stop_after_metadata=True` terminated
-download after the metadata frame (A5[7] in this capture) was received.
+download after A5[7] was received.
 
 **Channel identification note:**  The 4-2-26 blast saturated all four geophone channels
 to near-maximum ADC output (~32000–32617 counts).  Channel ordering [Tran, Vert, Long, Mic]
@@ -1188,22 +1187,15 @@ Two critical differences from `build_bw_frame`:
 > this equals `n * 0x0400` since `key4[2:4] = 0x0000`. The monotonic formula is correct
 > for all keys encountered on this device.
 
-The `stop_after_metadata=True` flag causes the loop to stop as soon as any needle in
-`_METADATA_FRAME_NEEDLES` is found in the A5 frame data, typically after 7–9 chunks.
-A termination frame is always sent before returning.
-
-**⚠️ CORRECTED 2026-04-15 — do NOT check only `b"Project:"`.** The single-needle check
-caused a critical waveform corruption bug: the metadata frame was decoded as ADC samples,
-making serial number bytes `"BE11529\0"` appear at sample ~929 followed by `0xFF 0xFF`
-fill, truncating the second half of every waveform.  Use `_METADATA_FRAME_NEEDLES` (see
-`protocol.py`) which includes `b"Geo: "` as the reliable universal anchor.
+The `stop_after_metadata=True` flag causes the loop to stop as soon as `b"Project:"` is
+found in the accumulated A5 frame data, typically after 7–9 chunks.  A termination frame
+is always sent before returning.
 
 #### 7.8.3 A5 Frame Layout
 
-Each A5 response frame contains a chunk of raw bulk data. One middle frame (position
-variable: fi==7 for blast events, fi==6 for desk-thump events) carries the compliance
-text block with project-info label-value pairs.  The `client` layer searches for ASCII
-labels with a null-terminated value read:
+Each A5 response frame contains a chunk of raw bulk data. Frame 7 of the stream carries the
+compliance text block with all project-info label-value pairs.  The `client` layer searches
+for ASCII labels with a null-terminated value read:
 
 ```
 "Project:"       → null-terminated project name
@@ -1211,10 +1203,9 @@ labels with a null-terminated value read:
 "User Name:"     → null-terminated operator name
 "Seis Loc:"      → null-terminated sensor location
 "Extended Notes" → null-terminated notes
-"Geo: "          → geo threshold (float string, in/s) — ALWAYS present
 ```
 
-All fields reflect the **setup at event-record time**, not the current device config.
+All five fields reflect the **setup at event-record time**, not the current device config.
 
 #### 7.8.4 End-of-Stream Behaviour and Chunk Timing