docs(permissions): re-anchor the system-context census after the provenance headers grew (#15302)

The three `isSystem` reads moved when the provenance-stamp headers were rewritten
(`email-template-provenance.ts:59` to `:77`, `sharing-rule-provenance.ts:47` to `:66`,
`webhook-provenance.ts:50` to `:68`) and `content/docs/permissions/system-context.mdx`
was not regenerated with them, so `check-system-context-census` reported 6 problems:
three read sites with no row, and three anchors that are no longer read sites.

This is the output of `node scripts/check-system-context-census.mjs --fix`, which
rewrote 3 anchors on 2 page lines. `--fix` REFUSED ZERO files, so this is a pure
line-number shift and not a population change. A second `--fix` run rewrites 0
anchors; the gate and its `--self-test` both exit 0.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XpTx2tbq3pZRYAdoGt6E6Y

Author: claude

content/docs/permissions/system-context.mdx

@@ -136,7 +136,7 @@ The largest single consumer — **17 of the 105 sites**.
 | 35 | `listShares()` skips the management gate | Get: full enumeration of who can see a record | `plugin-sharing/src/sharing-service.ts:1528` |
 | 36 | `sys_record_share` reads are **not** self-scoped | Get: tenant-wide share listing without `manage_sharing` | `sharing-plugin.ts:1088` |
 | 37 | Share-link policy `enabled` check bypassed; system callers re-enter under a system context | Get: link **creation** while the policy is off — resolution is **not** bypassed since #14033 (`publicSharing.enabled` is a standing policy held at every redemption): a link minted this way does not resolve until the block is enabled | `plugin-sharing/src/share-link-service.ts:469`, `:523`, `:527`, `:600`, `:630` |
-| 38 | Sharing-rule provenance stamp skipped | Lose: the row is not marked as an admin customization — seeder / `defineRule` / boot reconcilers are "the package door" | `sharing-rule-provenance.ts:47` |
+| 38 | Sharing-rule provenance stamp skipped | Lose: the row is not marked as an admin customization — seeder / `defineRule` / boot reconcilers are "the package door" | `sharing-rule-provenance.ts:66` |
 | 39 | Sharing-rule service write + delete paths return early | Lose: the manage-rules gate on the service surface, and the platform-global-rule delete guard | `sharing-rule-service.ts:202`, `:427` |
 
 ### 4. Approvals, reports, attachments, comments, knowledge
@@ -167,7 +167,7 @@ The largest single consumer — **17 of the 105 sites**.
 | 56 | Activation write / authoring refusals do not fire | runtime | Get: activation artifacts writable and authorable without the activation-authoring capability | `activation-gate.ts:138`, `:189` |
 | 57 | Automation run-state read, flow-authoring write and unrelated-screen read all pass | runtime | Get: run state, flow writes and screen reads with no grant | `domains/automation.ts:254`, `:545`, `:635` |
 | 58 | Audience-binding suggestion recording skipped | plugin-security | Lose: install-time suggestions are not recorded for system callers | `suggested-audience-bindings.ts:703` |
-| 59 | Email-template / webhook provenance stamps skipped | plugin-email, plugin-webhooks | Lose: the row is not marked as an admin customization | `email-template-provenance.ts:59`, `webhook-provenance.ts:50` |
+| 59 | Email-template / webhook provenance stamps skipped | plugin-email, plugin-webhooks | Lose: the row is not marked as an admin customization | `email-template-provenance.ts:77`, `webhook-provenance.ts:68` |
 | 60 | **Automation flow data nodes re-add the `owner_id` stamp** (the one place row 2's gap is compensated inline) | service-automation | Get: a flow-authored INSERT under system elevation still lands owned, when the run resolved a user. Fill-only — flow-authored values win | `runtime-identity.ts:279`, called from `builtin/crud-nodes.ts:319` |
 | 61 | Inbox caller refusal names `isSystem` as what was carried | service-messaging | Get: nothing — the refusal still fires. The flag only shapes the diagnostic, because privilege is not an authorization subject | `inbox-caller.ts:148` |