FABRIC-3.md: BMAPFMT flags bit values decided -- CLAIMED/MIGRATING/STALE

blk_meta_t's existing unused flags field (uint64_t) uses orthogonal bits,
not a mutually-exclusive enum: bit 0 = CLAIMED, bit 1 = MIGRATING (serves
MIGSM), bit 2 = STALE (serves UNCLEAN), 61 bits reserved. BMAPFMT's field
design (owner_fp, acl_allow, acl_ttl, and now these flags bits) is fully
decided; only the actual code edit to block_subsystem.h/.c remains.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

FABRIC-3.md

@@ -1782,21 +1782,24 @@ pubkey-based model — flagged, not silently reused.
                                   placeholder to fill reflexively. */
    uint64_t reserved_future;  /* untouched budget, same reasoning. */
    ```
-   `flags` (already existing, already generic) does double duty as the **state** field from
-   Step 1 — no new field, just future-defined bit values (`CLAIMED`/`MIGRATING`/`STALE`/etc.).
-   Everything else in `blk_meta_t` (`checksum`, timestamps, `content_type`, hash, chain links,
-   `app_data[15]`) is untouched.
+   `flags` (already existing, already generic, `uint64_t` on `blk_meta_t`, confirmed unused —
+   zero callers) does double duty as the **state** field from Step 1. **Bit values decided
+   2026-09-02**: orthogonal bits, not a mutually-exclusive enum — a block can be both
+   `CLAIMED` and `MIGRATING` at once. Starting set: bit 0 = `CLAIMED`, bit 1 = `MIGRATING`
+   (serves `MIGSM`), bit 2 = `STALE` (serves `UNCLEAN` — interrupted flush), remaining 61 bits
+   reserved. Everything else in `blk_meta_t` (`checksum`, timestamps, `content_type`, hash,
+   chain links, `app_data[15]`) is untouched.
 4. **Allocation granularity**: claims quantize to whole devblocks (3 Forth blocks), matching
    the existing packing — a cell never needs to describe partial-devblock ranges.
 
-**Resolved 2026-09-02 (part of item #1 below):** blocks need temporary elevation, reusing the
-same `ACL-TTL` mechanism as the word card, gated the same way by Zuse's eligibility list
-(§H.5) — see the `acl_ttl` field added above.
+**Resolved 2026-09-02:** blocks need temporary elevation, reusing the same `ACL-TTL`
+mechanism as the word card, gated the same way by Zuse's eligibility list (§H.5) — see the
+`acl_ttl` field added above. Also resolved same day: the `flags` bit values above.
 
-**Not yet scoped (deferred within this node):** the specific `flags` bit values for each
-state; whether `blk_get_meta()`/`blk_set_meta()` need new FORTH word wrappers or stay C-only
-like `zuse_cert_seed`'s "no FORTH access" precedent; the actual repurposing edit to
-`block_subsystem.h`/`.c` itself (this pass produced the field design, not the code change).
+**Not yet scoped (deferred within this node):** whether `blk_get_meta()`/`blk_set_meta()`
+need new FORTH word wrappers or stay C-only like `zuse_cert_seed`'s "no FORTH access"
+precedent; the actual repurposing edit to `block_subsystem.h`/`.c` itself — this pass (plus
+the `acl_ttl` pass before it) produced the full field design, not the code change.
 
 ### F.5 — `WIREBIND` (breadcrumb only — followed into `RUNCAP` instead, 2026-08-27)
 
@@ -3680,7 +3683,12 @@ became a 4-byte `acl_ttl` (mirroring `DictEntry`'s countdown shape) plus 3 bytes
 slack, kept lean rather than fully mirroring `DictEntry`'s `acl_mode`/`acl_pinned` too
 ("lean, TTL only" — a block isn't "pinned"/"strict" the way a word is).
 
-`BMAPFMT`'s field design (now including the TTL) is done but **the code change was never
+**`flags` bit values decided 2026-09-02**: `blk_meta_t`'s existing `flags` field (`uint64_t`,
+doubling as block state) uses orthogonal bits, not a mutually-exclusive enum. Starting set:
+bit 0 = `CLAIMED`, bit 1 = `MIGRATING` (serves `MIGSM`), bit 2 = `STALE` (serves `UNCLEAN`),
+remaining 61 bits reserved.
+
+`BMAPFMT`'s field design (TTL + flags bits) is now complete but **the code change was never
 made** — this refactor is presumably where it finally lands.
 
 ### H.7 — Messaging protocol groundwork (prerequisite to the message card)