chore: excrete 27 orphan integrated notes + 2 retrospective + 13 tombstones (-42 files)

Per "大刀阔斧" directive — Phase E of the foundation-laying cleanup.

The Phase A archive sweep deleted the v0_4_x/ and v0_5_x/ LANDED craft
sources; their PRE-INGESTED copies in .myco/notes/integrated/ were
left dangling — 27 notes whose `source:` frontmatter pointed at the
now-deleted craft files. This commit excretes those orphan notes:

- 12 stage-X handoff ingestions (stage_a/b1-b8/c)
- l0-identity-revision + v0-4-1-audit + agent-handoff-v0-4-0-v0-4-1
- n_20260510T145212Z (numbered 2..14, the v0.5.x craft batch)
- n_20260510T145212Z.md (the original v0_4_x/contract_audit ingest)

All 27 had `source: v0_4_x/...` or `source: v0_5_x/...` frontmatter
pointing at files deleted in Phase A. Reading them would have been
"these notes describe content recoverable from git history" —
pure noise.

Plus 2 distilled retrospectives whose `sources:` field listed only
the deleted notes above:
- d_v0-4-x-greenfield-rewrite-retrospective.md
- d_v0-5-x-discipline-and-fungal-vocabulary-retrospective.md

Plus 13 v0.5.x tombstones in .myco/notes/distilled/_excreted/
(myco excrete audit trail from 2026-04-19 → 2026-04-27, all pre-v0.6;
the audit-trail purpose was to track "this was deleted" while the
v0.5.x crafts were still operationally relevant — that era is now
over).

KEEP — verified:
- 16 integrated notes whose sources still exist (v0.6.x / v0.7.x /
  v0.8.x crafts at .docs/primordia/ top level, plus 2 agent-authored
  notes from glama-onboarding + v0.5.24 excrete-verb).
- 4 distilled retrospectives (v0.6.x / v0.7.x / v0.8.x / khazix-
  neat-freak); their `sources:` all resolve.

Immune impact: dropped from 7 baseline findings to **1** (just MB8
shim-telemetry). The 6 SE1 dead-link findings against the immutable
integrated notes are gone because the notes themselves went.

Gate: ruff/format/mypy clean, immune exit 0 with 1 baseline finding,
1608 pytest passed.

Net .myco/notes file count: 65 → 20 (-45 files including 27
integrated + 2 distilled + 13 tombstones + 3 directory cleanup).

Author: Yanjun