…ep 2c) (#46)

Step 2c of the RFC #42 migration plan. ByteRover's is_available()
only checked whether the brv CLI was on PATH — an operator with
brv installed but not logged in saw a false-positive green check
from doctor. health_check() now runs `brv status` to verify both:

  (True, "")                     — `brv status` exits 0.
  (False, "sdk_missing")         — brv CLI not on PATH.
  (False, "auth: ...")           — non-zero exit + stderr mentions
                                    auth / login / unauthorized /
                                    "not signed in" / 401 / 403.
  (False, "unreachable: timeout")— probe timed out.
  (False, "unreachable: ...")    — anything else (config issue,
                                    malformed install, etc.).

The probe has a 3-second timeout — `brv status` is local-cache
backed, so anything longer indicates a stuck CLI.

The "never raises" contract from the ABC default is preserved —
even if _run_brv itself propagates (it shouldn't; it has its own
try/except), the override catches the exception and returns
(False, "unreachable: <msg>").

Tests:
  - success returns (True, "")
  - sdk_missing when brv absent
  - 5 auth-classification cases (not-signed-in, Unauthorized,
    auth-required, 401, login required)
  - "timed out" → unreachable: timeout
  - generic non-zero exit → unreachable: <msg>
  - never-raises: even when _run_brv throws, returns tuple
  - long error messages truncated under 220 chars

Continues #42; does not close it. Three providers migrated:
mem0 (#44), honcho (#45), byterover (this PR). Six remain
before the doctor-branch collapse in step 3.

…s 2h + 3) (#52)

Closes #42. Final two steps of the RFC migration.

Step 2h — holographic health_check:
  Holographic is local-only (SQLite); no remote service. But a
  read-only HERMES_HOME (RO mount, wrong perms) would still
  break it at runtime. Override verifies db_path's parent
  directory is writable.

    (True, "")                     — parent mkdir + W_OK pass.
    (False, "unreachable: <msg>")  — mkdir failed or W_OK denied.
    (False, "config_error: <msg>") — get_hermes_home raised.

Step 3 — doctor branch collapse:
  Every shipped provider now implements health_check() with the
  RFC #42 reason-prefix taxonomy. The provider-specific Honcho +
  Mem0 elif blocks (~120 lines combined) are gone. The unified
  dispatch is one ~80-line block in doctor.py keyed on the prefix:

    healthy → check_ok("<name> reachable")
    no_api_key / no_credentials → _fail_and_issue (setup hint)
    no_url / no_endpoint        → _fail_and_issue (URL hint)
    no_config                   → check_warn (run setup)
    disabled                    → check_info
    sdk_missing                 → _fail_and_issue (plugin docs)
    auth:                       → _fail_and_issue (rotate key)
    not_found:                  → _fail_and_issue (verify base URL)
    http:                       → check_warn (unexpected status)
    unreachable:                → check_warn (transient hint)
    config_error:               → check_warn (config raised)
    health_check_raised:        → check_warn (provider bug; RFC
                                   #42 says health_check MUST NOT
                                   raise, so this is a contract
                                   violation worth flagging)
    other                       → check_warn (unknown verbatim)

Doctor's Memory Provider section is now ~80 lines instead of
~200, and adding the 9th provider requires zero doctor changes.

Migration table (8 providers total):
  mem0       — PR #44  GET /v1/memory profile
  honcho     — PR #45  get_honcho_client handshake
  byterover  — PR #46  brv status (CLI + login)
  supermemory — PR #48  client.profile probe
  openviking — PR #49  /health endpoint probe
  retaindb   — PR #50  /v1/memory/profile GET
  hindsight  — PR #51  mode-dependent (local import / cloud /version)
  holographic — this PR  db_path parent writability

Tests:
  - 6 new tests for holographic health_check
  - Updated 3 doctor tests to assert the new unified dispatch
    (auth → _fail_and_issue; unreachable → check_warn; healthy
    → "<name> reachable") instead of the now-removed elif-block
    output strings.
  - 228 health_check + doctor tests pass total.

The #42 RFC is now fully implemented across all shipped memory
providers. Closing the issue with this PR.