Add ESPHome display component; ring-buffer driver shared with PlatformIO

Driver (components/el512/el512_panel.*, ESP-IDF only):
- DMA ring of 8 x 4 lines (17 KB) refilled from the I2S EOF interrupt
  (IRAM) instead of a 142 KB full-frame stream; ~107 KB heap freed.
- 256-entry lookup table encodes 8 pixels per step.
- Back buffer + displayed buffer, swapped at the start of a frame.
- PlatformIO builds it via lib_extra_dirs (EL512Core); lib/EL512 keeps
  the Adafruit GFX front end.

ESPHome external component (platform: el512):
- DisplayBuffer with optional ENABLE / _LOWPWR pins, set_enabled(),
  set_low_power(), helper functions for page lambdas.
- still_alive_page: plays the Portal end-credits show, then returns to
  the previous page.

Still Alive engine moved to components/el512/still_alive.* with a built-in
5x7 font (from Adafruit GFX, BSD); the PlatformIO demo uses the same code.
The importer writes components/el512/still_alive_data.h and stops at 200 s
(--until-ms), matching the hand-trimmed data.

esphome/el512-panel.yaml: 8 pages (clock, forecast, agenda, dashboard,
now playing, Plex, solar, Still Alive), page select, rotation, display
and low-power switches, message text. home_assistant/packages/el512_panel.yaml:
helper template sensors for forecast, agenda, now playing and Plex streams.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tools/import_still_alive.py

@@ -3,14 +3,15 @@
 
 Reads index.html and res/stillalive.js from
 https://github.com/SDSkyKlouD/still-alive-web (downloaded, or local copies) and
-writes src/still_alive/imported.h, which the firmware uses instead of the
-placeholder lyrics.h / art.h / credits.h when it exists.
+writes components/el512/still_alive_data.h, the content of the Still Alive show
+(components/el512/still_alive.cpp) used by both the PlatformIO demo and ESPHome.
 
     python tools/import_still_alive.py                       # download from GitHub
     python tools/import_still_alive.py --html index.html --js stillalive.js
-    python tools/import_still_alive.py --out somewhere/imported.h
+    python tools/import_still_alive.py --out somewhere/still_alive_data.h
+    python tools/import_still_alive.py --until-ms 0  # keep the web version's outro too
 
-imported.h is committed with a disclaimer and source reference at its top.
+still_alive_data.h is committed with a disclaimer and source reference at its top.
 
 Source format: each <div class="container_lyrics" data-start=ms> is one screen
 (the console clears when it starts). Inside it, <span data-start data-dur
@@ -28,7 +29,11 @@ import urllib.request
 from pathlib import Path
 
 SOURCE_BASE = "https://raw.githubusercontent.com/SDSkyKlouD/still-alive-web/master/"
-OUT = Path(__file__).resolve().parent.parent / "src" / "still_alive" / "imported.h"
+OUT = Path(__file__).resolve().parent.parent / "components" / "el512" / "still_alive_data.h"
+
+# The show ends after the "... are property of their respective owners." line;
+# the web version's outro after it ("... is anyone there?") is left out.
+UNTIL_MS = 200000
 
 # Timing from stillalive.js.
 SONG_START_MS = 6750
@@ -146,12 +151,16 @@ def main():
     ap.add_argument("--html", help="local index.html (default: download)")
     ap.add_argument("--js", help="local res/stillalive.js (default: download)")
     ap.add_argument("--out", type=Path, default=OUT, help="output file (default: %(default)s)")
+    ap.add_argument("--until-ms", type=int, default=UNTIL_MS,
+                    help="drop steps starting at or after this time, 0 = keep all (default: %(default)s)")
     args = ap.parse_args()
 
     page = load(args.html, "index.html")
     arts = parse_art(page)
     art_ids = {name: i + 1 for i, name in enumerate(arts)}
     steps = parse_steps(page, art_ids)
+    if args.until_ms:
+        steps = [s for s in steps if s[0] < args.until_ms]
     credits = parse_credits(load(args.js, "res/stillalive.js"))
     if not steps or not arts or not credits:
         sys.exit("error: no lyrics, art or credits found; has the source changed?")
@@ -168,7 +177,7 @@ def main():
            "// owners. This project is not affiliated with or endorsed by Valve.",
            "//",
            "// Generated by tools/import_still_alive.py - do not edit by hand.",
-           "#pragma once", "", '#include "show_data.h"', ""]
+           "#pragma once", "", '#include "still_alive.h"', "", "namespace el512sa {", ""]
     for name, lines in arts.items():
         out.append(f"static const char* const ART_{name.upper()}_LINES[] = {{")
         out += [f"    {c_string(l)}," for l in lines]
@@ -187,7 +196,7 @@ def main():
     out += [f"static constexpr uint32_t SONG_START_MS = {SONG_START_MS};",
             f"static constexpr uint32_t CREDITS_START_MS = {CREDITS_START_MS};",
             f"static constexpr uint32_t CREDIT_CHAR_US = {CREDIT_CHAR_US};",
-            "static constexpr bool CREDITS_LOOP = false;", ""]
+            "static constexpr bool CREDITS_LOOP = false;", "", "}  // namespace el512sa", ""]
 
     args.out.write_text("\n".join(out), encoding="utf-8", newline="\n")
     screens = sum(1 for s in steps if s[3] == "STEP_CLEAR")