…vances #89 Direction A) (#98)

Operator-supplied intent override (Option A3 from #97). When
``HERMES_INTENT_OVERRIDE=code`` is set, the system prompt's
``stable`` layer narrows for tool-call-heavy traffic — addresses
#89's prompt-saturation symptom on mid-tier coding models.

## What narrows under code intent

| Block | Action | Why |
|---|---|---|
| SOUL.md | Skip | Largest single contributor; falls back to short DEFAULT_AGENT_IDENTITY floor |
| HERMES_AGENT_HELP_GUIDANCE | Skip | Off-topic for tool-call traffic |
| SKILLS_GUIDANCE | Skip | Per-tool block, off-topic for code |
| KANBAN_GUIDANCE | Skip | Worker-lifecycle, off-topic for code |
| SESSION_SEARCH_GUIDANCE | Skip | Off-topic for code |
| skills_prompt (the big one) | Skip | Biggest contributor when many skills loaded |
| MEMORY_GUIDANCE | **Keep** | Small + sometimes useful even for code |
| TOOL_USE_ENFORCEMENT_GUIDANCE | **Keep** | Critical for tool emission |
| Per-model operational guidance | **Keep** | Model-quality-specific |
| Env / platform hints | **Keep** | Execution-environment essentials |
| nous-subscription + computer-use + alibaba | **Keep** | Operational invariants |
| ``context`` + ``volatile`` layers | **Untouched** | Out of scope per #97 |

Other intents (``confer`` / ``planning`` / ``exploration`` /
``refinement`` / ``generic``) are recognized as valid but pass
through without narrowing in v1 (keeps the door open for per-
intent shape later).

## Intent vocabulary

Matches devagentic#240's ``intent_classifier`` 6-key enum exactly,
so the same operator-side classifier that's wired into devagentic's
R5 dispatch hook can also drive hermes-side prompt narrowing
without a second vocabulary.

## Doctor probe

New ``_check_intent_override_env`` probe surfaces the active
override at ``hermes doctor`` time — silent when unset, check_ok
when valid (with a narrowing-active note for ``code``), check_warn
with the full valid-keys list when typo'd. Mirrors the silent-
when-irrelevant pattern from PR #95 / #96.

## Tests

- 22 new prompt-narrowing tests in
  ``tests/agent/test_system_prompt_intent_override.py``: resolver
  enum + normalization (5), per-section drops under code (7),
  pass-through for non-code intents (5), typo falls back (1),
  byte-count regression (1), default-still-includes counter-case (1),
  case-insensitive (1), runtime-vs-doctor-config sanity (1).
- 6 new doctor-probe tests in
  ``tests/hermes_cli/test_doctor_intent_override_probe.py``:
  silent-when-unset / silent-when-empty / code-ok-with-narrowing-note /
  non-code-valid-pass-through / typo-warn-with-valid-sample /
  case-insensitive.
- 258 total green across affected suites (system-prompt + prompt-
  builder + restore + doctor + provider-env + tools-subset). No
  regression in the existing prompt-shape pins.

## Composition note

Option A1 (port classifier) + A2 (devagentic GraphQL surface) are
deferred per the #97 sequencing — A3 unblocks deployment-specific
narrowing immediately; A1/A2 only matter when dynamic per-turn
classification is needed on the hermes side. The classifier output
on the devagentic side (NousResearch#240) drives R5 dispatch decisions there.