chore: the compiler is a build input too, and regenerate under the fixed elc

Installing the fixed compiler exposed a blind spot in this gate. On clean main,
with no source changed, soulc-stamp reported OK while the committed amalgam had
gone stale by a line — because the fingerprint covered .el sources and not the
toolchain that turns them into dist/soul.c. That is exactly the class of silent
divergence the gate was written to close, and it had it.

The stamp now fingerprints the elc binary alongside the sources. Demonstrated: with
the old stamp the gate passed after a compiler swap; with this change the same
condition fails, naming __compiler__.

dist/soul.c regenerated under the installed compiler (1,205,027 bytes) and verified:
builds from its own committed input, the declared principal is present in the
resulting binary, interface 110 routes in / 110 out.

Differential evidence that the new compiler is a strict superset — same sources,
both compilers:
  neuron soul        1 differing line, the el_cgi_init emission
  engram server.el   0 differing lines
  mcp-wrapper        0 differing lines
  mcp-proxy          0 differing lines

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

dist/soul.c.stamp

@@ -1,7 +1,8 @@
 # soul.c.stamp — fingerprint of the .el sources dist/soul.c was generated from.
 # Written by tools/soulc-stamp.sh --write. Do not hand-edit.
-# generated_amalgam_sha256 ee09798ad93ddd047136577cf324483e5956984d60d06596d34662f315ee0df4
-# generated_amalgam_bytes  1204845
+# generated_amalgam_sha256 f251307717d40796a8909154fc7077d3343a0d30e20889b7e9d16f1c4308a888
+# generated_amalgam_bytes  1205027
+7cf5e29d2618db2fca04e6df7aa8954dd6cf9ac5e70aafb8e0b52aa734882131  __compiler__
 f8597e10546654bce3fbbe40461b2da59d0e06dbf1b038d1d362d24f949e3911  awareness.el
 b6f3d14ca0c26017a2d617399a6d3754dabb0905e4d5f52eb75d25c4ad18d3c5  chat.el
 42288c212cbf72fb1e8ecbd4d9900e4e9ee1cfa475b7974295c7637f1bf2939f  elp-input.el