docs(agent-notes): consolidate superseded decisions

.agents/notes/implemented/feature/2026-07-16-durable-per-step-time-context.md

@@ -12,13 +12,13 @@ A process-local refresh cache makes displayed time depend on state that cannot s
 
 ## Decision
 
-`@deepseek-ai/dsh-time-context` is an opt-in function plugin in `packages/context/time-context/`. It registers a prepended `agent/pre-step` listener and, when an injection is due, calls `agent.inject()` for a pre-step attempt whose signal is not already aborted. The injected `context/message` carries source `{ kind: 'plugin', plugin: 'time-context' }` and append surface metadata; a suppressed attempt appends nothing.
+`@deepseek-ai/dsh-time-context` is an opt-in function plugin in `packages/context/time-context/`. The `context/` group holds bounded request-context enrichments that define neither a tool nor a service, and shipped examples do not mount this plugin because its time-zone disclosure and token cost are deployment policy. It registers a prepended `agent/pre-step` listener and, when an injection is due, calls `agent.inject()` for a pre-step attempt whose signal is not already aborted. The injected `user/message` carries source `{ kind: 'plugin', plugin: 'time-context' }` and append surface metadata; a suppressed attempt appends nothing.
 
 The listener records preparation context before a possible `step/start`. Its prepended registration runs before ordinary automatic compaction listeners, so pressure estimation and any resulting surface rewrite observe a newly appended reading. A later pre-step listener can cancel or fail the attempt before the step opens; the reading remains because the durable log is append-only and this plugin performs no rollback.
 
 The optional `timeZone` config resolves the Node process's IANA zone once at plugin load when omitted; an explicit value is validated by `Intl.DateTimeFormat`. The timestamp includes the numeric UTC offset and resolved IANA zone.
 
-The optional `refreshIntervalMs` config is manually validated at plugin load as a non-negative safe integer. Omission or `0` injects on every eligible preparation attempt. A positive value scans the raw session events for the most recent `context/message` with this plugin's source and injects when none exists, wall time moved backward, or the event is at least the configured age. The raw event timestamp governs even after compaction shadows the message, so scheduling persists across turns and process resume without a timer or process-local cache.
+The optional `refreshIntervalMs` config is manually validated at plugin load as a non-negative safe integer. Omission or `0` injects on every eligible preparation attempt. A positive value scans the raw session events for the most recent `user/message` with this plugin's source and injects when none exists, wall time moved backward, or the event is at least the configured age. The raw event timestamp governs even after compaction shadows the message, so scheduling persists across turns and process resume without a timer or process-local cache.
 
 ### Text and elapsed baselines
 
@@ -29,7 +29,7 @@ Time sampled while preparing turn <turn>, step 1: <timestamp>
 Elapsed since the preceding model-visible message: <duration-or-unavailable>.
 ```
 
-The baseline is the latest preceding user, assistant, tool-result, context, or steering message. This includes the accepted prompt that opened an ordinary message turn. If no model-visible message exists, the duration is `unavailable`.
+The baseline is the latest preceding user, assistant, tool-result, or steering message. This includes the accepted prompt that opened an ordinary message turn. If no model-visible message exists, the duration is `unavailable`.
 
 An injected later-step reading is:
 
@@ -48,11 +48,7 @@ The plugin contributes nothing to system-prompt assembly. `request/header` conta
 
 ## Testing
 
-Unit and real-loop tests pin formatting, both elapsed baselines, interval omission and zero, threshold boundaries, cross-turn and per-session scheduling, backward-clock behavior, invalid config, resumed raw-event lookup after compaction, aborted-signal behavior, later-listener cancellation and failure, listener disposal, source and surface metadata, cumulative multi-step visibility, and absence from request headers. A keyless subprocess e2e boots the real Loader and stdio app, drives two turns, and verifies the persisted context events externally.
-
-## Supersedes
-
-This decision supersedes the dynamic system-prompt storage and refresh policy in [Optional time-context plugin](2026-07-14-time-context-plugin.md). It keeps the package location, opt-in deployment stance, timestamp formatting, process-zone default, and load-time validation. Durable history replaces the `context:time` prompt section, process-local refresh cache, and request-header deltas; `refreshIntervalMs` controls durable append frequency instead of prompt replacement.
+Unit and real-loop tests pin formatting, both elapsed baselines, interval omission and zero, threshold boundaries, cross-turn and per-session scheduling, backward-clock behavior, invalid config, resumed raw-event lookup after compaction, aborted-signal behavior, later-listener cancellation and failure, listener disposal, source and surface metadata, cumulative multi-step visibility, and absence from request headers. A keyless subprocess e2e boots the real Loader with the Headless composition, drives two ordered one-shot turns, and verifies the persisted plugin-attributed messages externally.
 
 ## Alternatives considered
 
@@ -61,10 +57,13 @@ This decision supersedes the dynamic system-prompt storage and refresh policy in
 - **Inject from a background timer** — rejected because idle time has no pending request to consume the value, and timer-driven injection would create durable turns solely to report time passing.
 - **Expose time only through a tool** — rejected because ordinary temporal reasoning would require an avoidable tool round trip and would not guarantee a reading before every step.
 - **Use `agent/session-prefix`** — rejected because one loop-instance prefix cannot represent distinct step timestamps and does not accumulate historically attributable readings.
+- **Mutate assembled requests or register independent prompt variables** — rejected because request-local insertion bypasses the durable surface and separate providers can sample different instants. One attributed context message records the timestamp and elapsed baseline atomically.
+- **Default to UTC or add a time-zone detection dependency** — rejected because an explicitly mounted plugin follows its process environment unless the operator selects an IANA zone, while no server-side library can infer a remote user's zone.
+- **Mount the plugin in shipped compositions or place it in `core/`** — rejected because disclosure, time zone, freshness, and history cost are deployment choices for an optional context leaf, not product-spine policy.
 
 ## Consequences
 
 - Omission or `0` records every eligible preparation attempt; a positive interval reduces append frequency and history growth while preserving durable scheduling across resume.
 - Timing context remains append-only until compaction shadows older surface nodes, including a preparation reading left by a later cancellation or failure.
 - The first-step duration normally measures from the prompt that opened the turn, while later-step durations measure model and tool processing since the preceding step context.
-- An omitted `timeZone` still reflects the deployment process rather than a remote user, and elapsed time still uses durable harness append boundaries rather than client-origin timestamps.
+- An omitted `timeZone` still reflects the deployment process rather than a remote user, and elapsed time still uses durable harness append boundaries rather than client-origin timestamps. Supporting client-origin time requires a separate durable input contract.