Introduces watch/, a real Pebble watchapp (built via pebble build) that

shows the daily tarot/astrology reading on-device: persistence, reading
computation, and UI screens, driven by the existing engine/interpreter
code linked in unchanged where possible.

Required engine-side changes to make that linking work:
- A compact low-precision ephemeris (lowprec_ephemeris.c) replacing the
  vendored ~127KB Astronomy Engine, which doesn't fit the watch's ~64KB
  app budget.
- Hand-rolled sqrt/atan2/sin/cos replacements for that ephemeris and
  astro.c's Ascendant calculation - Pebble's statically-linked libm
  hard-faults on real hardware under this app's -fPIE link for all four.
- narrative.c/guidance.c refactored from FILE*/fprintf onto snprintf-
  based buffers, since Pebble's SDK blocks fprintf at compile time.

watch/scripts/gen_i18n_tables.py

@@ -0,0 +1,105 @@
+#!/usr/bin/env python3
+"""Generates watch/src/c/i18n_tables.auto.c from engine/i18n/*.lang.
+
+Compiles each non-English .lang file into a `static const char *const`
+keys[]/values[] pair for i18n_load_table() (see engine/src/i18n.h's own
+doc comment on why the watch needs a zero-copy, compiled-in table
+instead of i18n_load()'s file-based parsing). English is deliberately
+skipped: the fallback text already baked into tarot_data.c/astro.c/
+narrative.c/guidance.c *is* English, so shipping a redundant English
+catalog would roughly double this app's translation-data footprint
+(which counts against the same ~64KB whole-app budget as everything
+else - see watch/README.md) for zero behavioural benefit.
+
+This is a generated file (like message_keys.auto.c, resource_ids.auto.c
+elsewhere in a Pebble project) - not meant to be hand-edited or
+committed; watch/wscript regenerates it on every build. Parsing rules
+mirror engine/src/i18n.c's i18n_load() exactly: '#'-prefixed and blank
+lines are skipped, the first '=' splits key/value, and both sides are
+trimmed of surrounding spaces/tabs only (not quotes - values are raw
+text, same as the desktop file loader).
+"""
+import glob
+import os
+import sys
+
+SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__))
+I18N_DIR = os.path.normpath(os.path.join(SCRIPT_DIR, "..", "..", "engine", "i18n"))
+OUT_PATH = os.path.normpath(os.path.join(SCRIPT_DIR, "..", "src", "c", "i18n_tables.auto.c"))
+
+
+def parse_lang_file(path):
+    entries = []
+    with open(path, "r", encoding="utf-8") as f:
+        for raw_line in f:
+            line = raw_line.rstrip("\r\n")
+            stripped = line.strip(" \t")
+            if not stripped or stripped.startswith("#"):
+                continue
+            if "=" not in line:
+                continue
+            key, value = line.split("=", 1)
+            key = key.strip(" \t")
+            value = value.strip(" \t")
+            if not key:
+                continue
+            entries.append((key, value))
+    return entries
+
+
+def c_string_literal(s):
+    escaped = s.replace("\\", "\\\\").replace('"', '\\"')
+    return '"' + escaped + '"'
+
+
+def main():
+    lang_files = sorted(glob.glob(os.path.join(I18N_DIR, "*.lang")))
+    languages = []
+    for path in lang_files:
+        code = os.path.splitext(os.path.basename(path))[0]
+        if code == "en":
+            continue  # see module doc comment - English is never a compiled table
+        languages.append((code, parse_lang_file(path)))
+
+    lines = []
+    lines.append("/* Generated by watch/scripts/gen_i18n_tables.py from engine/i18n's .lang")
+    lines.append(" * files - do not edit by hand, and do not commit (see .gitignore). */")
+    lines.append("")
+    lines.append('#include "i18n_tables.h"')
+    lines.append("")
+    lines.append('#include "../../../engine/src/i18n.h"')
+    lines.append("")
+    lines.append("#include <stddef.h>")
+    lines.append("#include <string.h>")
+    lines.append("")
+
+    for code, entries in languages:
+        lines.append(f"static const char *const k_keys_{code}[] = {{")
+        for key, _ in entries:
+            lines.append(f"  {c_string_literal(key)},")
+        lines.append("};")
+        lines.append(f"static const char *const k_values_{code}[] = {{")
+        for _, value in entries:
+            lines.append(f"  {c_string_literal(value)},")
+        lines.append("};")
+        lines.append("")
+
+    lines.append("void watch_i18n_load(const char *lang_code) {")
+    for code, entries in languages:
+        lines.append(f'  if (lang_code && strcmp(lang_code, "{code}") == 0) {{')
+        lines.append(f"    i18n_load_table(k_keys_{code}, k_values_{code}, {len(entries)});")
+        lines.append("    return;")
+        lines.append("  }")
+    lines.append("  i18n_load_table(NULL, NULL, 0); /* \"en\" or unrecognized: use built-in English */")
+    lines.append("}")
+    lines.append("")
+
+    os.makedirs(os.path.dirname(OUT_PATH), exist_ok=True)
+    with open(OUT_PATH, "w", encoding="utf-8") as f:
+        f.write("\n".join(lines))
+
+    print(f"wrote {OUT_PATH} ({', '.join(code for code, _ in languages)})", file=sys.stderr)
+
+
+if __name__ == "__main__":
+    main()