feat: sampling knobs + live PTY stream-json + token UI (v2.7.3)

Three small wins from boocode_code_review_v2 §1 #11/#7/#8.

#11 sampling knobs: top_n_sigma + dry_* family as first-class Agent fields,
threaded into the request body via providerOptions.openaiCompatible. Fixes a
latent bug — top_k (rejected by the AI-SDK provider) and min_p (never passed to
streamText) were dead on the wire; both now route through the same channel.
--reasoning-budget documented in data/AGENTS.md.

#7 live PTY stream-json: new stream-json-parser.ts line-buffers qwen/claude
NDJSON and emits text/reasoning/tool frames live + persists, with a fallback to
the old opaque slice. claude gets --output-format stream-json --verbose.

#8 token UI: agent_sessions input/output_tokens/cost now flow through the route
+ type and render beside the AgentComposerBar session chip.

Built by 3 parallel agents. Server 523 + coder 245 tests passing; builds + web
tsc clean. Builds on v2.7.2. openspec sampling-streamjson-tokens.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

data/AGENTS.md

@@ -6,6 +6,10 @@ Operating rules for every agent in this registry. Full procedures live in the `c
 
 **Worktrees** — Isolate work in a worktree when it is parallel to in-progress work, risky/experimental, a hotfix interrupting other work, or splits into independent units — just create when clear, propose in one line when ambiguous, skip quick/small single-stream work. Branch from a stable base (default branch); worktrees persist (never auto-remove or auto-merge); they isolate code state, not runtime (ports/DBs/services still collide). Full heuristic: invoke `using-worktrees`.
 
+**Sampling knobs** — Each `## Name` frontmatter block accepts these per-agent sampler fields, threaded into the llama-swap chat-completion request: `temperature`, `top_p`, `top_k`, `min_p`, `presence_penalty`, and (v2.6) `top_n_sigma`, `dry_multiplier`, `dry_base`, `dry_allowed_length`, `dry_penalty_last_n`. The `top_n_sigma` + `dry_*` repetition family curb the doom-loop-prone local model. Omit a field to leave it at the server default. Example: `top_n_sigma: 1.0`, `dry_multiplier: 0.8`, `dry_base: 1.75`, `dry_allowed_length: 2`, `dry_penalty_last_n: -1` (-1 = whole context).
+
+**Reasoning budget** — To cap a reasoning model's thinking tokens, pass `--reasoning-budget` through `llama_extra_args` (already permitted by the deny-list validator; routes the agent to llama-sidecar). Example frontmatter line: `llama_extra_args: ["--reasoning-budget", "2048"]`. This is a sidecar process flag, not a chat-completion body param — distinct from the sampling knobs above.
+
 ## Code Reviewer
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 temperature: 0.6