Fix caller lineup never loading and add Wellspring cult callers

The lineup fix and the new characters both land in main.py, so they share a
commit rather than being split artificially.

Lineup fix — populate_backgrounds() was reachable only through
POST /api/session/reset, so taking calls without hitting reset left
session.caller_backgrounds empty for a whole show. Every caller got a hollow
prompt, collapsed into generic relationship filler, and Silas lost his lore.
Now start_call populates on demand, get_caller_prompt raises
EmptyCallerBackgroundError instead of emitting an empty prompt, /api/callers
reports lineup readiness to a header badge, and cross-episode topic dedup
widened from 2 shows to 10.

Wellspring callers — Doyle as the anchor defector plus a six-member pool,
grouped by new frontmatter fields (group, group_lead, group_weight, register,
explicitness). A faction is capped at one caller per show, with a 15% roll for
two pairing the lead with one other member. group_weight lets an anchor carrying
an arc get slots faster than texture characters.

Also detects model refusals, which arrive as ordinary 200s and previously
reached air as broken-character text or dead silence.

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

docs/plans/2026-08-15-wellspring-callers-design.md

@@ -0,0 +1,172 @@
+# The Wellspring Callers — Design
+
+**Date:** 2026-08-15
+**Status:** Approved, not yet implemented
+
+## Problem
+
+Silas is the show's strongest recurring character, but he is the only window into
+The Wellspring — and he controls the framing entirely. He describes a warm
+commune of seekers. Nobody contradicts him. The bit is funny but static, and the
+cult has no weight because there are no stakes the audience can see.
+
+## Goal
+
+Add callers from inside The Wellspring who offer perspectives Silas does not
+control — including frightened ones — so the commune becomes a place with real
+consequences rather than a running gag. Keep Silas playable as comedy.
+
+## Structure
+
+An **anchor** character with a progressing arc, plus a **pool** of rotating
+members for fresh angles.
+
+- The anchor carries continuity and escalating dread.
+- The pool supplies variety and prevents the counter-perspective from
+  flattening into one note.
+- Silas remains the leader's version of events.
+
+## The anchor: Doyle
+
+```yaml
+name: Doyle
+voice: Grant        # plain, tight — deliberate contrast with Silas's Sebastian
+age: 47
+group: wellspring
+register: dry, understated, factual
+explicitness: low
+```
+
+Two years in. Joined eight months after his divorce, when a member sold him soap
+at a farmers market in Las Cruces and asked him a question nobody had asked him
+in a year. He runs the soap kettles — twelve-hour days, physical, unglamorous.
+
+The soap room is the engine of the character: **it is where the money is, and
+nobody spiritual pays attention to it.** He sees shipping manifests, deposit
+slips, whose names are on which accounts. He is not a seeker. He is the guy who
+fixes the pump.
+
+**His fear is specific.** He is not afraid of being hurt. He is afraid of being
+right. He has a truck, a CDL, and nowhere to be — he could leave tomorrow, and
+has been telling himself that for eleven months. What frightens him is that he
+keeps not leaving and can no longer tell whether that is his choice.
+
+**Calling mechanic.** No signal at the Terlingua property. Doyle calls from town
+on supply runs — a gas station lot in Study Butte, engine running, twenty
+minutes before someone notices the truck has been gone too long. This caps call
+length naturally, explains why he cannot talk long, and gives the host a ticking
+clock. An abrupt hangup is in character, not a failure.
+
+**Register.** He describes appalling things in the flat voice of a man reading a
+parts list. The comedy and the dread come from the same place: he does not
+editorialize.
+
+## The pool
+
+Six members, each an ordinary regular file, drawn one at a time.
+
+| Member | Voice | Age | Register | Explicitness |
+|---|---|---|---|---|
+| Renata — true believer | Celeste | 34 | Radiantly happy, evangelical, funny | high |
+| Alvin — bookkeeper | Conrad | 61 | Dry, precise, funny-then-cold | low |
+| Junie — grew up there | Pippa | 19 | Guileless, no frame of reference | low |
+| Ford — fourteen days in | Levi | 28 | Love-bombed, evangelical, too fast | medium |
+| Marguerite — wants out | Marlene | 58 | Exhausted, practical, sad | medium |
+| Cyrus — inner circle | Damon | 41 | Charming, then not | medium |
+
+**Junie is a fixed constraint.** Someone who grew up inside the commune is the
+show's darkest available note, and she works precisely because nothing explicit
+ever attaches to her. Her horror is that she believes all of it is normal. Her
+`explicitness: low` is not a default — it does not change.
+
+## Tone
+
+Mostly unsettling-but-comic, with the capacity to go genuinely dark. The
+Wellspring should carry real weight without every call being heavy. Register is
+assigned per character rather than globally, so the true believer plays funny in
+the same season Doyle plays frightening.
+
+**Adult content.** The show is adult and the Wellspring's sexuality is already
+load-bearing in canon. Characters may talk frankly about sex and kink. This is
+controlled per character via `explicitness: low | medium | high` rather than a
+global switch, so explicitness varies by who called and the show does not
+flatten into wall-to-wall smut.
+
+**The one hard separation: consensual weirdness and coercion stay in different
+lanes.** An openly horny commune with elaborate rituals is the comedy. Silas
+pressuring a member into participating is the horror — that is where the weight
+comes from. Blurring them casually makes the show mean rather than dark and
+makes Silas irredeemable, which costs the character. Existing canon already
+handles this correctly: his 2026-03-15 reckoning treats the coercion as real
+harm.
+
+## Selection mechanics
+
+Current behavior (`backend/main.py`, `_build_backgrounds`): every active regular
+draws independently at `min(1.0, 0.4 + 0.3 × shows_missed)`, then the list is
+truncated to 3.
+
+Adding eight Wellspring files to that would let the commune eat every regular
+slot. So:
+
+1. Partition regulars by the new `group` frontmatter field.
+2. Ungrouped regulars behave exactly as today.
+3. Within `group: wellspring`, members draw on their existing per-member
+   probability, then the group is **capped**:
+   - **1** Wellspring caller per episode normally
+   - **2** on a 15% roll — a "both sides tonight" episode
+   - On a two-night, prefer Silas plus one non-Silas member
+4. Group cap applies before the global 3-regular truncation.
+
+## Data flow
+
+```
+~/code/dotfiles/regulars/*.md   (+ silas/silas.md)
+    ↓ regulars_v2.load_all_active_regulars()
+    ↓   Regular gains: group, register, explicitness
+    ↓ _build_backgrounds()  — group partition + cap
+    ↓ regulars_included
+    ↓ caller_gen.build_batch_prompt()  — renders register + explicitness
+    ↓ Sonnet 4.6 batch
+    ↓ session.caller_backgrounds
+    ↓ get_caller_prompt()  — live dialog
+```
+
+Touch points:
+
+- `regulars_v2.py:29` `load_regular()` — parse four new frontmatter fields
+  (`group`, `group_lead`, `register`, `explicitness`), defaulting so existing
+  files keep working
+- `regulars_v2.py:19` `Regular` dataclass — four new fields
+- `main.py` `_build_backgrounds()` — group partition and cap
+- `caller_gen.py:132-138` — render `register` and `explicitness` into the batch
+  prompt (currently renders only name, lore, arc_state)
+- Eight new markdown files; one frontmatter line added to `silas.md`
+
+## Failure mode to guard
+
+Model refusals do not look like errors. `llm.py:385-395` handles exceptions and
+empty completions by returning `None` with a printed message, but a content
+refusal typically arrives as a **200 with refusal text**, which flows through as
+ordinary dialog and breaks character on air — or as an empty completion that
+reads as dead air.
+
+Add explicit detection so a refusal is visibly distinct from a caller who simply
+had nothing to say, surfaced in the host's log rather than only stdout. Without
+this, tuning `explicitness: high` upward has no feedback signal.
+
+## Testing
+
+- `load_regular()` parses the new fields; files lacking them still load
+- Group cap holds: 8 Wellspring regulars never yield more than 2 in a lineup
+- Two-night rate approximates 15% over many seeded draws
+- On a two-night, Silas is preferred plus exactly one non-Silas member
+- Ungrouped regulars are unaffected by group logic
+- Batch prompt contains `register` and `explicitness` for each included regular
+- Junie's `explicitness` is `low` (guards against a careless edit)
+
+## Out of scope
+
+- Arc progression automation — arc_state stays hand-edited, as today
+- Promotion of pool members to anchors
+- Any change to how walk-in callers are generated