Give the interpreter real Celtic Cross meanings and --format/--lang support

- guidance.c now prints last, after the full spread; both it and main.c's
  new Celtic Cross readout pull real Waite card meanings via tarot_data.c
  instead of just naming cards.
- interpreter-cli gains --format text|html|json and --lang en|de, matching
  deck-engine - required linking engine/src/tarot_data.c and i18n.c into
  the interpreter binary (a narrow, documented exception to its earlier
  "no engine .c files" policy) and writing German translations for
  narrative.c's/guidance.c's own text.

interpreter/src/guidance.h

@@ -0,0 +1,60 @@
+#ifndef DECK_GUIDANCE_H
+#define DECK_GUIDANCE_H
+
+#include <stdio.h>
+
+/* Header-only dependency on the engine for struct/enum *definitions*,
+ * same policy as narrative.h/significance.h - see their comments for
+ * why. Unlike those, though, the root Makefile *does* link
+ * engine/src/tarot_data.c's *implementation* (tarot_card_name()/
+ * tarot_card_meaning()) into the interpreter binary - a deliberate,
+ * narrow exception; see the Makefile's own comment on
+ * INTERP_TAROT_TEXT_OBJS for why that doesn't compromise this module's
+ * independent testability. */
+#include "../../engine/src/tarot.h"
+#include "significance.h"
+
+/* Ties the day's single most significant transit
+ * (interp->top_items[0]) to the Celtic Cross spread, and prints a short
+ * paragraph of concrete guidance on how to meet the day - the "combined
+ * storytelling" piece docs/reading.md flags as future work, now built.
+ * Prints on every day, quiet or major, tailored to interp->day_level -
+ * callers can invoke it unconditionally after every
+ * interpret_daily_reading() call.
+ *
+ * The core guidance keys off two things: the character of the top
+ * transit's aspect (harmonious/discordant/neutral, same classification
+ * narrative.c uses) and whether the spread's Attitude position - Waite's
+ * "Himself: his position or attitude in the circumstances", the
+ * position most directly about how the reader is meeting the day - fell
+ * upright or reversed. That crossing (3 x 2 = 6 combinations) is
+ * original text written for this project, not drawn from Waite or
+ * Sepharial, since neither source discusses combining astrology and
+ * tarot; it stays valid regardless of the day's intensity. What *does*
+ * vary with interp->day_level is only the sentence introducing the top
+ * transit (e.g. "With Saturn as today's dominant influence" on a Major
+ * day vs. "Saturn is only faintly active today, but for what it's
+ * worth" on a Quiet one). A day with no aspects in orb at all
+ * (interp->top_item_count == 0, always DAY_QUIET) has no transiting
+ * planet to introduce, so it falls back to a stance keyed on the
+ * Attitude card's orientation alone.
+ *
+ * The paragraph also names the Attitude and Outcome cards and, via
+ * tarot_card_meaning(), states their actual Waite meaning for the
+ * orientation they landed in (e.g. what Wheel of Fortune reversed
+ * means) - not a duplicated table, the real thing, since tarot_data.c
+ * is linked (see above).
+ *
+ * Every piece of this module's own text (stance/intro/no-transit/label
+ * strings) is looked up via i18n_get() under "guidance.*" keys
+ * (engine/i18n's .lang files) before falling back to the English text baked
+ * into guidance.c, so it respects whatever --lang the caller loaded
+ * with i18n_load() (main.c does so before calling this). The German
+ * guidance.intro.* templates are deliberately phrased so the planet
+ * name placeholder is always the sentence's grammatical subject
+ * (nominative case) across all four day levels - see guidance.c's own
+ * comment on k_intro_fallback. */
+void guidance_print(FILE *out, const char *indent, const DailyInterpretation *interp,
+                     const CelticCrossSpread *spread);
+
+#endif