refactor(workflows): extract discuss-phase modes/templates/advisor for progressive disclosure (closes #2551) (#2607)

* refactor(workflows): extract discuss-phase modes/templates/advisor for progressive disclosure (closes #2551)

Splits 1,347-line workflows/discuss-phase.md into a 495-line dispatcher plus
per-mode files in workflows/discuss-phase/modes/ and templates in
workflows/discuss-phase/templates/. Mirrors the progressive-disclosure
pattern that #2361 enforced for agents.

- Per-mode files: power, all, auto, chain, text, batch, analyze, default, advisor
- Templates lazy-loaded at the step that produces the artifact (CONTEXT.md
  template at write_context, DISCUSSION-LOG.md template at git_commit,
  checkpoint.json schema when checkpointing)
- Advisor mode gated behind `[ -f $HOME/.claude/get-shit-done/USER-PROFILE.md ]`
  — inverse of #2174's --advisor flag (don't pay the cost when unused)
- scout_codebase phase-type→map selection table extracted to
  references/scout-codebase.md
- New tests/workflow-size-budget.test.cjs enforces tiered budgets across
  all workflows/*.md (XL=1700 / LARGE=1500 / DEFAULT=1000) plus the
  explicit <500 ceiling for discuss-phase.md per #2551
- Existing tests updated to read from the new file locations after the
  split (functional equivalence preserved — content moved, not removed)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(#2607): align modes/auto.md check_existing with parent (Update it, not Skip)

CodeRabbit flagged drift between the parent step (which auto-selects "Update
it") and modes/auto.md (which documented "Skip"). The pre-refactor file had
both — line 182 said "Skip" in the overview, line 250 said "Update it" in the
actual step. The step is authoritative. Fix the new mode file to match.

Refs: PR #2607 review comment 3127783430

* test(#2607): harden discuss-phase regression tests after #2551 split

CodeRabbit identified four test smells where the split weakened coverage:

- workflow-size-budget: assertion was unreachable (entered if-block on match,
  then asserted occurrences === 0 — always failed). Now unconditional.
- bug-2549-2550-2552: bounded-read assertion checked concatenated source, so
  src.includes('3') was satisfied by unrelated content in scout-codebase.md
  (e.g., "3-5 most relevant files"). Now reads parent only with a stricter
  regex. Also asserts SCOUT_REF exists.
- chain-flag-plan-phase: filter(existsSync) silently skipped a missing
  modes/chain.md. Now fails loudly via explicit asserts.
- discuss-checkpoint: same silent-filter pattern across three sources. Now
  asserts each required path before reading.

Refs: PR #2607 review comments 3127783457, 3127783452, plus nitpicks for
chain-flag-plan-phase.test.cjs:21-24 and discuss-checkpoint.test.cjs:22-27

* docs(#2607): fix INVENTORY count, context.md placeholders, scout grep portability

- INVENTORY.md: subdirectory note said "50 top-level references" but the
  section header now says 51. Updated to 51.
- templates/context.md: footer hardcoded XX-name instead of declared
  placeholders [X]/[Name], which would leak sample text into generated
  CONTEXT.md files. Now uses the declared placeholders.
- references/scout-codebase.md: no-maps fallback used grep -rl with
  "\\|" alternation (GNU grep only — silent on BSD/macOS grep). Switched
  to grep -rlE with extended regex for portability.

Refs: PR #2607 review comments 3127783404, 3127783448, plus nitpick for
scout-codebase.md:32-40

* docs(#2607): label fenced examples + clarify overlay/advisor precedence

- analyze.md / text.md / default.md: add language tags (markdown/text) to
  fenced example blocks to silence markdownlint MD040 warnings flagged by
  CodeRabbit (one fence in analyze.md, two in text.md, five in default.md).
- discuss-phase.md: document overlay stacking rules in discuss_areas — fixed
  outer→inner order --analyze → --batch → --text, with a pointer to each
  overlay file for mode-specific precedence.
- advisor.md: add tie-breaker rules for NON_TECHNICAL_OWNER signals — explicit
  technical_background overrides inferred signals; otherwise OR-aggregate;
  contradictory explanation_depth values resolve by most-recent-wins.

Refs: PR #2607 review comments 3127783415, 3127783437, plus nitpicks for
default.md:24, discuss-phase.md:345-365, and advisor.md:51-56

* fix(#2607): extract codebase_drift_gate body to keep execute-phase under XL budget

PR #2605 added 80 lines to execute-phase.md (1622 -> 1702), pushing it over
the XL_BUDGET=1700 line cap enforced by tests/workflow-size-budget.test.cjs
(introduced by this PR). Per the test's own remediation hint and #2551's
progressive-disclosure pattern, extract the codebase_drift_gate step body to
get-shit-done/workflows/execute-phase/steps/codebase-drift-gate.md and leave
a brief pointer in the workflow. execute-phase.md is now 1633 lines.

Budget is NOT relaxed; the offending workflow is tightened.

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

get-shit-done/workflows/execute-phase/steps/codebase-drift-gate.md

@@ -0,0 +1,79 @@
+# Step: codebase_drift_gate
+
+Post-execution structural drift detection (#2003). Runs after the last wave
+commits, before verification. **Non-blocking by contract:** any internal
+error here MUST fall through and continue to `verify_phase_goal`. The phase
+is never failed by this gate.
+
+```bash
+DRIFT=$(gsd-sdk query verify.codebase-drift 2>/dev/null || echo '{"skipped":true,"reason":"sdk-failed"}')
+```
+
+Parse JSON for: `skipped`, `reason`, `action_required`, `directive`,
+`spawn_mapper`, `affected_paths`, `elements`, `threshold`, `action`,
+`last_mapped_commit`, `message`.
+
+**If `skipped` is true (no STRUCTURE.md, missing git, or any internal error):**
+Log one line — `Codebase drift check skipped: {reason}` — and continue to
+`verify_phase_goal`. Do NOT prompt the user. Do NOT block.
+
+**If `action_required` is false:** Continue silently to `verify_phase_goal`.
+
+**If `action_required` is true AND `directive` is `warn`:**
+Print the `message` field verbatim. The format is:
+
+```text
+Codebase drift detected: {N} structural element(s) since last mapping.
+
+New directories:
+  - {path}
+New barrel exports:
+  - {path}
+New migrations:
+  - {path}
+New route modules:
+  - {path}
+
+Run /gsd:map-codebase --paths {affected_paths} to refresh planning context.
+```
+
+Then continue to `verify_phase_goal`. Do NOT block. Do NOT spawn anything.
+
+**If `action_required` is true AND `directive` is `auto-remap`:**
+
+First load the mapper agent's skill bundle (the executor's `AGENT_SKILLS`
+from step `init_context` is for `gsd-executor`, not the mapper):
+
+```bash
+AGENT_SKILLS_MAPPER=$(gsd-sdk query agent-skills gsd-codebase-mapper 2>/dev/null || true)
+```
+
+Then spawn `gsd-codebase-mapper` agents with the `--paths` hint:
+
+```text
+Task(
+  subagent_type="gsd-codebase-mapper",
+  description="Incremental codebase remap (drift)",
+  prompt="Focus: arch
+Today's date: {date}
+--paths {affected_paths joined by comma}
+
+Refresh STRUCTURE.md and ARCHITECTURE.md scoped to the listed paths only.
+Stamp last_mapped_commit in each document's frontmatter.
+${AGENT_SKILLS_MAPPER}"
+)
+```
+
+If the spawn fails or the agent reports an error: log `Codebase drift
+auto-remap failed: {reason}` and continue to `verify_phase_goal`. The phase
+is NOT failed by a remap failure.
+
+If the remap succeeds: log `Codebase drift auto-remap completed for paths:
+{affected_paths}` and continue to `verify_phase_goal`.
+
+The two relevant config keys (continue on error / failure if either is invalid):
+- `workflow.drift_threshold` (integer, default 3) — minimum drift elements before action
+- `workflow.drift_action` — `warn` (default) or `auto-remap`
+
+This step is fully non-blocking — it never fails the phase, and any
+exception path returns control to `verify_phase_goal`.